That was my first thought, but it doesn't work given my understanding of the question. It provides the package where the method was compiled, and that's not necessarily the class/package that provides the method.

$ perl -le'
   { package Role; use Moose::Role; sub m {} }
   { package Class; use Moose; with "Role"; }
   use Sub::Identify qw( stash_name );
   print stash_name( Class->new->can("m") );
'
Role
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Your method returns Role even though Class->new->m() would call Class::m. find_implementor returns Class.