I really don't see an issue with the rooflines. Looks like the angles are fairly similar and the clean lines of both structures should be easy to coordinate, especially in your open, rural setting. Since you've found a stunning deal, I would say, go for it! I definitely would want to find an architect ASAP and by all means, before you pour the slab, make sure you have a plan to coordinate.

A few simple steps can give your room a lot more vibe! Try pairing the drapes with sheer curtains, that will give the window more depth. The tv wall could be your accent wall, a dark blue would actually work very well. If the TV has backing, I would hang it on the wall, a few inches above the furniture piece. The two frames above the white dresser should go below the wall clock. Instead, a large art piece (about the length of the dresser) would complement that wall much better. I would also replace the coffee table with a rectangular, heavier glass and metal table, placed in the center. Also pillows. Pick up colors from your art work and the accent wall and use those to find pillows to decorate your sofas. Hope this inspires :-)

Oh wow, it looks fantastic! The black looks so striking against the white, not too sharp at all. Congratulations on the house, you must be very excited to move in. :)

Looks like the palm tree look is working so I would blend that with some succulents maybe agave which can grow large and make great statement plants. Also stick with the stones.