if it is actually in the roof then it is likely starlings or house sparrows- you may get swallows in there if the entry is big enough... but no matter what is nesting there NO-ONE is by law allowed to disturb ANY bird at its nest site.
By this stage of the nesting season it is likely that most birds will have laid, hatched and be well on the way to fledging a first brood. No guarantees that they will have flown yet- though your ears will tell you if they have gone.
However- many birds will then go on to lay a secong clutch of eggs and raise a second brood.
If this is the case then look up the RSPB and speak to them about the legal situation- you will find that if the birds are at the nest then the work cant be done til the nesting season is over.