Welcome to the new and improved Proflex / K2 Tech Forum!
Are the roots you encounter wet? If so then it's the tire.
I am always skeptical when I hear someone say that one tire is better than another on wet roots because in my experience, the only tires that ACTUALLY grip on wet roots are ones with metal studs. Other than that, your best bet is to try to either hit all roots perfectly perpendicular or VERY carefully.My 2 cents...