Check if user, of an ADGroup, belongs to specific RoleAssignment

Question

Best way to check if an user (not the current user), inserted in a ADGroup, belongs, or not, to SPList/SPWeb RoleAssignments?

Impersonate an use the .ContainsCurrentUser method, brings access denied issues.

getting the SPGroup:

foreach (SPPrincipal oPrincipal in from SPRoleAssignment oRoleAssignment in roleAssignmentCollection select oRoleAssignment.Member)
{
   try
   {
       SPGroup oRoleGroup = (SPGroup)oPrincipal;
       (...)
}

...and in PS Scripting? Any clue?