Scrape the excess paint out of the roller using the curved edge of the painters knife. This excess paint is fine and should be put back in the can.
Wash the bulk of the paint out by running under warm water and "squeezing" the paint down from one end to the other. Continue doing this until the water is running fairly clear.
Stand the roller on its edge and let the water run into the open end so that is "cascades" over the edge. Let it run for several minutes, gently "squeezing" the water down towards the bottom. The water will run clear after a few minutes.
If you don't have a spinner, then just allow to sit in sink on edge after wringing water out by hand.