I planted common milkweed once, but in a spot that didn’t matter, and it’s still here.…. the stems are easy to pull out, but I’ve never dug to check on the rhizomes. Seems to be a tough survivor kind of plant, so I think it will work in pots and just do the best it can with whatever conditions you give it.

Milkweed grows well in deep pots. (tap root)

I've had them return when planted in very large pots. Mine are plastic, and the size of half whiskey barrel planters. I had them in a rather contained area of the garden (not in pots) and I think it will be years until those rhizomes are actually gone...if ever!