What Yosemite compatible tool may I use to perform rotoshaping?

I recently found out the hardest way that Shake cannot be launched anymore on Yosemite.😮

This really annoys me as I learnt to love that genius piece of (however visually ugly) software.

I will especially miss the rotoshaping feature which more than once allowed me to replace the background behind one of my actors.

Do someone know if FCPX or MotionX may have this feature?

If not, what could I use (possibly cheap but I should not dream)?

Thanks in advance.