Thank you for the comments and suggestions. My video card is fine. It is an ATI Radeon HD 7800 series with 2 GB memory and the latest firmware. The roof was auto-built by HD although I'm sure it could use some tweaking.
The main issue according to Tech Support was the size of the Terrain, which was too large. I deleted the existing terrain and then rebuilt it as a smaller size. The rendering artifacts disappeared immediately and entirely.
Thank you,
Buzzsaw827
Home Designer Architectural 2015
Windows 7 Pro 64 bit
Buzzsaw827's post in Rendering Artifacts in Perspective Full Overview was marked as the answer