is it true with rotoscoping you could have a video where two people embrace for a hug at a park, select them out of the video, then insert them into a different video with a forest and running waterfall, and now you will have two people embracing for a hug with a running water fall in the background, when you pay the video? as well little parts from the oringal clip but im sure that can be resolved with content aware fill?
Everything is possible with patience. Rotoscoping it's probably the right approach here, but it does take time going over the tracks and adjusting them. Once you've cut out the huggers, I'd suggesting rendering them out so that the rotoscope tool doesn't tie up your resources.
Once you replace the background, you'll need to spend a bit of time matching the colours with the background, adding some foreground element to distract from the cutout etc... keep your shot short, so the audience doesn't have time to spot any issues too.
Rotoscoping is used to create an animated matte or mask to isolate something in the frame. Your two actors would be a perfect example. Depending on the shot, you may need to motion stabilize or create multiple masks to efficiently rotoscope by hand. The shot may be handled better using Mocha AE or even Rotobrush, AE's automated roto tool.
Here's a simple Rotoscoping tutorial I put together a long time ago. It simply demonstrates the use of multiple masks and motion stabilization.
We can probably point you in the right direction if you can share the shot or a frame from the shot with a good description of what happens in the scene, including camera moves. I often use multiple techniques on the same shot. I've used everything from Mocha AE, plus masking by hand as I demonstrated in the video above, plus Rotobrush and even a procedural matte (keying) on the same shot to get the results I needed. You rarely can get away with using only one tool to create the kind of composite you describe.