I have done this before, but it's been a few years. We were traveling on our return BGR-BOS-CVG-TUL, but I needed to go to ATL. I had work buy a BOS-ATL flight and I just hopped on that once I got to BOS. We both had no issues at all. That was in 2008, so things in their system could have changed to allow them to detect this more readily, but I doubt it.
Why not have work buy you ROA-CVG-SEA?