Roots can be a tough obstacle, and difficult to negotiate if they are large, off angle, or wet.
The problem you can have is after you lift your front wheel over them, the rear wheel may slide along the front or top of the root and pitch the bike over sideways. As you approach the root, keep a 90 degree angle, speed up slightly, pull the front wheel up and over the root, and then lunge your upper body forward for added momentum to bring the rear wheel up and over. Be prepared for the rear tire to slide sideways a little as it goes over the root. Several roots in a row require concentration, good balance, and timing.