I am in the United States, but such a force sounds awesome!
In the new edition of Warhammer, you can actually mix and match various armies as long as they have at least one Faction keyword that matches up. If I was doing a Rogue Trader force, I'd run a Vanguard of Inquisition (so your Rogue Trader gets all the neato Inquisition stuff, and a retinue of infinitely customizable goons in the Acolyte entry). A benefit of using an Inquisitor is they can go in damn near any Imperium transport, so if you wanted your super ostentatious Rogue Trader to drive around in a golden Land Raider Cathedral you could have that, or if he wants to quietly land with little fanfare in an Arvus Lighter, you can have that, or any transport in between. It's cool and fluffy, in my opinion. Yet another reason an Inquisitor might work as a Rogue Trader is if you use the generic "Ordo" rules (rather than taking an Inquisitor from a specific existant Inquisitorial Ordo), then you get "re-roll 1's against characters" as your ability, which fits with how I imagine a rogue trader might fight - a duelist, consummate in general fighting but not necessarily a battlefield warrior himself.
Once you've gotten your Rogue Trader, his assistants, his retinue, and his ride, then you have a bewildering array of Imperial assets to choose from for your next detachment. You could bring Imperial Guard, representing hired mercenaries/private security/literally anything, or Space Marines, if the Rogue Trader joined a crusade and got swept up in the action, or Adeptus Mechanicus, if he's working on a mining operation to secure resources...
...literally anything Imperial. The world is at your fingertips!