No. They haven't released it for the US versions yet, so unless a rom has that feature, you can't do it. There is like 5 roms out there right now and none of them are anywhere near implementing features like that without some kind of code from Samsung yet.
Once they release a version with multitasking. You will be able to root the device and it will still work. If you load a different rom after that then it depends on the rom.