Hello. I've been reading Rogue Trader and so far I haven't noticed it talking about shuttles or fighter craft. Am I just blind or is it not there? I would love to know what tiny ships are aboard my PCs ship and to what use they can be used to.

Personal vehicles like Aquilas and Guncutters are covered in Into the Storm, and fighter craft (along with torpedoes) are covered in Battlefleet Koronus.

Ok. I will look into those books. Thank you!

If you're just using them narratively the only thing you really need to know is that there's an average of "1 lighter per 5 space" on a starship and that they vary in size from (roughly) a Star Trek Shuttle to a two-story Millennium Falcon, depending on size of Voidship and role. Most transport Voidships, however, are intended to be loaded and unloaded by void-dock, not lighter.