[GAP Forum] degree <5 univariate polynomials solving

[Dima Pasechnik]

Dear Forum,
I need to diagonalize medium-size (say, 30x30, with 0-1 entries)
symmetric integer matrices
that have at most cubic Z[x]-factors in their minimal polynomials.

I found out about radiroot package, but I cannot find a way to use
it to use the roots of solvable polynomials it can find in my 
computation (so that I can call, say, Eigenvectors() with the 
right field). 
Am I missing something?
 
thanks,
Dmitrii