Roots[lhs==rhs, var] yields a disjunction of equations which represent the roots of a polynomial equation.
Roots uses Factor in trying to find roots. You can find numerical values of the roots by applying N.
Roots can take the following option:
Roots is generated when Solve and related functions cannot produce explicit solutions. Options are often given in such cases.
Roots gives several identical equations when roots with multiplicity greater than one occur. See The Mathematica Book on the web: Section 1.5.7 and Section 3.4.1. See also: Solve, NSolve, FindRoot, ToRules, Factor, InterpolatingPolynomial.
Roots[lhs==rhs, var] yields a disjunction of equations which represent the roots of a polynomial equation. 
