There is no requirement for fire-hoods or for fire-rated downlighters unless you are perforating a fire compartment boundary, and as these will actually be in the roof you are clearly not doing that.
Holes in plasterboard in a roof will impact on fire spread in terms of Parts B3 (structure) and if applicable B4 (external fire spread) of the b/regs.
So precautions need to be made whether its a roof or not