Connecting my roof

Can anyone help - i built our first floor in one file and the roof in another. I removed the roof by creating a group then imported the roof into the other file but I cant get the roof to merge with my new first floor?
does that make sense?

As always, it would be helpful if you could share the file(s) showing your problem. That said, could you expand on what you mean by “merge”?

Sadly file too big to upload, due to furniture & me not using layers.

Ive tried to upload a screen shot
The roof just wont slide into place. This is as close as I can get before it pings past were I want it to stop?

You have the option of using a file sharing service (Dropbox, Google Drive,etc.) to upload your large skp file here. Just remember to include the url address so that other Forum participants can locate and open your file.

If you can put the move tool on the bottom corner vertex of the roof (not an arbitrary position), the inferencing should snap it to position to the corner on the building. You may have to move around to see it without interference , or go to wireframe view to more easily see those points?

It’s not really relevant to your question, but you seem to misunderstand SketchUp’s layers. Having used layers would have nearly no effect on your file’s size, as they affect what is visible on the view but do not reduce, prune, or otherwise organize the model contents.