Final Cut Pro 7: Jump back, keep playing
In Final Cut Pro 7, you can control playback while you edit marker information. To start and stop, you use Control-Space Bar. There are a few more shortcuts that are useful and one that works when you aren’t editing a marker.
It is useful for when you are reviewing your work: to jump back in units of the Pre-Roll value, press Control-Command-Space Bar. The advantage with this as opposed to Shift-Back Arrow to move back 1 second is that shortcut stops playback. With this Pre-Roll Back command, the sequence keeps playing from the earlier point.
To set the Pre-Roll value, go to the Editing tab of the User Preferences window (from the ‘Final Cut Pro’ menu):
This is good if you want to do ‘one last review’ of the edit you’ve just finished and go on from there. It also is helpful if you think you’ve missed something.
alex4D old blog 
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I want if is there any shortcut for post roll forward
I have the same question as Omkar! Any way to jump forward?
Sorry no. You can’t jump forward and keep playing. If you use Shift-forward arrow to go forward 1 second, the movie stops playing. To jump forward 6 seconds and play, you’ll need to type ‘+’ ‘6’ ‘.’ Return Space
Wish apple would fix this. but thanks for the quick reply!