How can I make curved gingerbread sheets for a gingerbread house?
Not knowing your recipe too well I’ll assume a gingerbread with a rollable and cuttable texture, like for gingerbread men. 

I would use a few empty cans with a slightly smaller diameter than your tower design. 

If you cut the can(s) lengthwise in thirds or so, you can drape rectangular strips of dough over them with only some bend, which will put only little  gravitational stress on the soft dough during baking. Make sure that the total width of the segments is more than the 360 degrees circle to allow for shrinkage and some extra to cut the edges to fit.

Bake the dough on the molds (with a layer of parchment, ideally) and let the parts cool on the tins as well. 

Assemble as you would for the straight walls. A spare can can help keep the parts upright and in shape until the icing “cement” has hardened.