Don't forget that it hugely depends on who the Rogue Trader is fighting as well.

Arriving on a feral or fuedal world and the armsmen would effectively be very well armed troops and even general ratings could be useful if push came to shove.

On a world with a higher tech level and untrained soliders are likely to be as much of a liability as anything else.

Personally I would be wary of allowing the Rogue Trader too many elite/well trained troops unless they have invested heavily in terms of Profit Factor/Requisition into them. Afterall you want the Rogue Trader and his officers to be doing most of the leg work.

I would say as standard there should be 0.1% of the crew should be good well trained oathsworn and then maybe 1% who are soldiers. Then a further 10% who are armsmen. Able to hold thier own against inferior troops and probably able to use various weapons but closer to police/militia than soldiers and would probably have other functions on the ship as well..

On a Cruiser sized ship this would give you (pop: 90,000 aprox) this would give you

90 Elite soldiers

900 Soldiers

9000 armsmen

I find that armsmen, household troops, and carried troops tend to be very different beasts.

Armsmen are like your ship's police force, your Adeptus Abites on board. You probably don't want them mowing down your crew because the cooks got hold of some wonky rye flour, so they are probably mostly armed with shock mauls or something.

The household guards are usually your choice boarding troops so they probably have shotguns, hand cannons, assault stubbers, and other high-volume short-ranged weaponry with low penetration, along with lascutters, meltas and other such to get through bulkheads.

Carried troops are IG types, equipped with a variety of weapons to deal with a variety of situations - AT RANGE, like the Imperial Guard is supposed to do. Basilisks are good for this, too. I personally like the cheap versions, the towed Earthshaker cannons, but that's the RT in me talking. We like doing things on the cheap.

I'll have you know I spare no expense! On the cheap, pfft. *grumbling*

What I do in the games I've run is as follows:

100 storm-trooper equivelents as a household guard per PC (I leave it up to the PCs whether this is the rogue trader's guard or if they have their own units each (generally the coghead and the navigator will have their own and everyone else lumps theirs together).).

1% of crew/permenant passengers as security troopers (basically permentant under arms troops who have a security/police role most of the time, armed with light solid projectile weapons (autoguns/heavy stubbers/shotguns), flak armour, shock mauls and gas grenades).

5% of crew/permenant passengers as armsmen who when the ship is at battle stations their duty is to be ready to board/repel boarders as needed, very lightly armed (stub/auto pistols, shot guns, maybe the odd stub rifle or so on, tools and hand weapons, maybe a flak vest but just their work gear otherwise).

I say for barracks that they can hold a medium infantry brigade equivelent (with light infantry counting as half, heavy infantry/mech infantry/tanks/artillery counting double (I also say that tanks and artillery do not give a boost to boarding/hit and run not even if you are mad enough to try to run earthshakers through the corridors of your ship!) with the idea being that barracks contain space for the troops to bunk and do at least some basic training (like target practice, PT, combat drills and so on), as well as hold their supplies, camp followers and so on. I also say by default they are able to easily ship their men and equipment to where they are needed to disembark reasonably rapidly (as I'm assuming that the designers of the ship arn't stupid enough to put their armoured unit storage at the wrong end of a maze of corridors). I also do allow units to be counted as light infantry regardless of type but their gear will be kept in the hold and so they will take much longer to deploy and they won't get any bonuses for training from the barracks (I give players the oportunity to upgrade the skill level of troops through training in the barracks.

In my games I also have a house-ruled type of ship called a light ship (basically think of them as being either very large support craft or very small escort/transport/utility ships without warp capability so relies on a carrier ship rather like a smaller version of the tau orca/warden classes (I got the idea after reading a book about naval vessels in the 1920s-1950s which had things like torpedo boat and seaplane carriers)) some of which can transport troops (either by design or by bodging), with the cutters (a multi-role master of none type) able to land a single infantry company without vehicles, the heavy drop ships (a heavy lander as the name suggests) able to land 3 infantry companies and their vehicles (double if light infantry due to the lack of vehicles) or 2 mechanized infantry companies or 1 armoured or artillery company at a time or the heavy barge which can land double the amout of the heavy drop ship but is a flying unarmoured brick (it is made for carrying cargo rather then troops but can be pressed into this role if necessary but is a big slow high value target so only use for this role if you have already secured your landing ground or if you don't like your soldiers very much). I am currently playtesting these rules but if people want them they can have them.

I have a hard time with starting figures and don't think I've run (or run in) 2 games alike in that department. Ships having 10% armsmen is just too many, and 1% just isn't enough. I lean toward 5%. In my next game I'm going to give the Dynasty household guard based on starting PF and see how that works. Like Bron, I also give each PC a number of NPCs as companions, though I'm less generous. Bodyguards either use the bodyguard or companion stats, and PCs have to flesh out their whole party with the numbers given. For Navigators, that means their relief; for Astropaths, that means their choir. I also require families to come out of that same number and severely frown on orphan-stories. Hey, I'm tired of snowflakes. Your momma thinks you're unique, and that's enough.

And Filliman, I'm a huge fan of towed artillery pieces. Colonies tend to be compact. They need a starport and ground defense installations. Those can usually be covered from a central position, so self-propelled pieces aren't needed. For mobile strike forces, I like to reply on airmobile troops supported by valkyries and marauders, so basilisks are not necessary unless a major campaign is expected. Towed pieces, on the other hand, are in constant demand.