Often a rootbound plant can be pulled easily from the pot.
The second step is to get a plant out of its pot. If a plant is rootbound, it helps to water the root ball thoroughly in advance. For plants in small to medium pots, invert the pot and support the top of the root ball with one hand. Put your other hand on the bottom of the pot and use a downward throwing motion with an abrupt stop. Many plants will slip out after one or two throws. If not, knock the edge of the pot against a sturdy surface, such as a potting bench, still holding the pot with both hands. It may take a few good whacks to release the plant; be careful not to break the pot.
A plant ready for repotting should slide out with the soil in one piece. If much of the soil falls free of the roots, the plant may not need repotting. If it does, there will likely be a solid soil-and-root mass in the shape of the just-removed pot. Roots should be white or light-colored. Black, dark-colored, or foul-smelling roots are usually signs of a serious problem, such as fungal disease.