The new Rotobrush 2.0 does improve the spline you draw or brush to outline what you need to separate from the background. However, in the latest updates, the propagation and freeze steps hang up on long frame scenes. After much searching on the forums other users have found we need to uninstall the updates for After Effects and go back to 18.1. I just did that and now Rotobrush 2.0 is performing naturally!
Shawn Briscoe commented
That's great James! I will upgrade when this is available. Thank you!
James Landy commented
We recently fixed several performance issues when using Roto Brush. The fixes are currently in Ae 22.1 beta, and soon to be released in Ae 22.0.