I think it's not worth the trouble. True, FastTrack is a great system and Ross switches are probably the best in the O-gauge market. But, together I see nothing but trouble.
Fast Track needs Fast Track switches and Ross switches needs either Ross or Gargave track.
I wouldn't say they "need" each other. I've used Ross switches with Tubular track (Marty Fitzhenry does the same) as well as Atlas track. No issues once you get everything level and the proper transition track/pins. Lee Willis has done a very nice layout with Atlas track and Fastrack switches, built ON TOP OF existing Fastrack!
I agree it is not worth the trouble...plus Fastrack switches are excellent quality.
Fastrack switches are very reliable and work well. There is no need to get Ross switches when using FastTrack, unless you need a switch that Lionel does not make. The Fastrack line is pretty extensive. If you really want Ross, I would look at their Tinplate switches. They will most likely mate a lot easier with Fastrack and should be the same height.