You only get one role at a time because the search was limited to the 'friend' role. To change that you need to change the 'where' criteria in the 1st hashref:

$c->model('DB::Users')->search_like(
    { 'username' => '%foo%' },
    {
        join => { 'map_user_role' =>  'role'  },
        '+select' => [ 'role.id', 'role.role' ],
        '+as'     => [ 'roleid', 'role' ],
        rows => 10, 
    },
);
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The plus ("+") sign is needed because 'role.id' and 'role.role' do not originate in the Users schema/table