1. I can't reproduce the problem. I tried the trim with both Trim to Roof Command and using Solid Element Operations (SEO). Sometimes SEO results aren't always what you expect. For example if you trimmed with SEO, but the operator was not included in the module, then when the module is placed in another file there will be no trim.
Is this the only trim that did not survive the module?
Can you post a screenshot, it might give us a clue as to what went wrong.
In the meantime, you did redo the trim in the site file.
2. Do the files have matching material attributes?
Options> Element Attributes> Attribute Manager
If you created the building material(s) in the building file, you need to add them, via Attribute Manager, to the site file.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"