Rotoscoping can be a pain and can take a very long time, but there are some things you can do that will help to speed up the process.
First, rather then using a single mask for the entire object, split it into several parts and roto each piece separately. For instance if you are working on a person, use separate masks for the head, arms, chest, legs, etc. It may seem like more work, but it makes it much easier to edit and manipulate your masks, especially if the subject has a lot of movement.
Second, make your masks on separate solid layers, rather then having them all on the video layer. This way you can easily turn each piece on and off. To apply the roto, just pre-compse your masked solids and use it as the track-matte for the video layer.
Third, track the piece you are going to rotoscope before you start. If you can't use After Effects' tracking tools, just do a quick track by hand by animating a null object. Moving one point around is much easier then all those mask points and it will save you a lot of time. Once you have your track, apply it to the solid that your mask will be on. Now, when you rotoscope, you wont have to move your points as far to get them in position.
Last, rather then rotoscoping each frame one by one, do the first frame, then do the last frame. Once those keyframes are in place, go the the middle and correct the matte there. Continue moving back and forth throughout your composition correcting the mask on whichever frame it is furthest from where it should be. After correcting the mask where it most needs it, you will notice that the mask says close if not exactly where it needs to be without having to set every single frame.
Doing these four things will help you rotoscope faster while maintaining accuracy. Give them a try the next time you have to do it.