All you need is a photo editing package that can open a .flm file. Something like Photoshop maybe.
Export your footage as a .FLM file, open in Photoshop and draw away. Plenty of tutorials about if you look but a quick guide follows on the end of this post.
Once your 'rotoscoping' is complete, save back to the .flm file and import the .flm file back into Premiere. hey presto, it's done. For a slam dunk, over ina second, this shouldn't take you more than an evening
Quick Light Sabre guide.
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Open .FLM file in Photoshop.
Do this for each frame
Select the area to be the light sabre. Should be easy in this case, just a circle.
Cut and paste the selection so it appears as a new layer.
Paint the new layer flat white ( all light sabres are white, it's only the glow that changes colour)
Go into layer properties for the 'white bit'. Select outer-glow and choose your colour and amount of glow.
Do all this for each frame.
Flatten the resulting image. Save back as a .flm - done.
I'd keep a working copy of your work as a .PSD though.