Display message depending on capability outside loop

Use global $authordata:

Testing for roles:

global $authordata;    

if ( in_array( 'administrator', $authordata->roles ) )
{
   echo 'Hello Admin!';
}
elseif ( in_array( 'editor', $authordata->roles ) )
{
    // echo something else
}

Or testing for capabilities:

if ( ! empty ( $authordata->allcaps['manage_options'] ) )
{
   echo 'The author can manage options';
}
elseif ( ! empty ( $authordata->allcaps['edit_others_posts'] ) )
{
    // echo something else
}