Can I declare Keyan as PS12 using Roark's pilot ability at the beginning of the combat round then use Swarm Tactics upgrade that Keyan has to bring the blue squad up to 12 in the combat phase as well if I declare it in that order?

Provided that Keyan and Blue are at range 1 and Roark/Keyan are within range 1-3 of each other?

Yes.

You can definitely do that. You could have Keyan Swarm Tactics Roark up to PS12 if you'd rather as well.

Against low to medium PS ships could have Roark bring the Blue up to PS12 and Keyan bring Roark up to PS7 so your whole squad is shooting first.

I've used Roark, Cracken and Blount to screw with an Imperial ace build. Opponent forgot Roark's ability and two of his ships suffered serious damage due to 3 Zs dumping missiles at R2. Clusters on Cracken allowed 2Zs to add Target Locks to join the Focus tokens they had. Blount with Assault Missiles was frosting on the cake.

So I could actually have a Rourk, Keyan and Ten Numb flying together at range 1 with Swarm on both the b's so that Rourk bumps up to 12 as well and all 3 ships shoot first?

Basically Rourk puts Keyan up to 12 first. Keyan uses swarm tactics to bump Ten up to 12 and then Ten uses swarm tactics to bump Rourk up to 12. All within range 1 of each other.

I considered switching out blue for Ten, hence the 3 x 12.

Yes, it works, but you end up spending both your EPTs to do it, which is a VERY high opportunity cost. And it only works if you keep your entire force together at r1 of each other.