RollBack Rx does support dual boot. However, you need to install the GUI component onto both OS partitions and only the subconsole on your first OS setup. You may want to follow the following KG article instructions on multi-boot installation:
Does RollBack Rx support Multi-boot systems?
Keep in mind that you will need to select CUSTOM installation during your setup.
With regards to selecting partitions in a dual boot configuration - this is not possible. RollBack Rx will need to protect the entire contents of the root drive in this type of config.