I have no real knowledge except that Bouganvillea is planted against house walls all over Southern Europe. But building techniques might be different.

You haven't posted your area, so it's difficult to say how vigorous the plants may grow for you.
"Old fashioned" bougs grow to almost tree-like proportions in warmer climates, with something for support, but the newer cultivars are much more restrained.
I would say that the roots are no worse than those of a rose - certainly large but not invasive as water-seeking tree roots might be.
I would check out the depth of your foundations, ANYTHING can penetrate under, and seek professional advice as it's better to spend $100 and shift a new plant, than pay thousands in house repairs.
I don't think there is any advantage in a raised pot in the same position if the roots will eventually go into the ground.

Bougainvillea roots tend to be long and brittle and they break easily if the ground they are growing in is disturbed in any way.