$MaxRootDegree specifies the maximum degree of polynomial to allow in Root objects.
Evaluation of Root objects with high degree minimal polynomials may be slow:
The result is a valid algebraic number with minimal polynomial proven irreducible:
Root does not attempt factoring polynomials with degrees higher than $MaxRootDegree:
The result is not a valid algebraic number:
Root RootReduce Solve Cubics Quartics