Rotobrush goes slow

Before we can give you meaningful workflow suggestions we need to see the shot you are working with. Most beginners don't take the time to figure out what part of the shot is going to end up in the final edit. In 1919 it wasn't at all uncommon to have shots in movies that lasted for 20 or 30 seconds, but today the average time between shots is more like something between 3 and 7 seconds. My average comp is under 7 seconds. If you really need to separate the actor (you) from the background for all 30 seconds of your shot the first part of the workflow is to figure out what you can do to simplify the rotoscoping. More often than not you can use a combination of masks and procedural mattes to reduce the workload. 

Show us your shot and we can probably come up with a way to simplify the work. Almost all of the mattes I create are a combination of multiple effects and many times, multiple layers. The trick to making this kind of work efficient is to plan the shot. 

Without any system info about your computer nobody can gauge whether this is normnal or not. From slow harddrives hampering fiel I/O and cahcing the roto frames to deeper issues with a CPU not supporting certain math processing extension to something as trivial as a driver on your system having replaced a wrong DLL or being outdated this could be anything. Much more info is required to even come close to unriddling this.

Mylenium