Connecting a specific USER ROLE to a specific POST TYPE

I want to connect a specific user role (Contacts) to a CPT (Deals). your documentation says to do this

add_action( 'mb_relationships_init', function () {
    MB_Relationships_API::register( array(
        'id'   => 'users_to_posts',
        'from' => array(
            'object_type' => 'user',
            'meta_box'    => array(
                'title'       => 'Assigned To',
                'field_title' => 'Select Deals',
            ),
        ),
        'to'   => array(
            'object_type' => 'post',
            'post_type'   => 'post',
            'meta_box'    => array(
                'title'         => 'Managed By',
                'context'       => 'side',
                'empty_message' => 'No users',
            ),
        ),
    ) );
} );

2 questions:

1. the object_type is set to user, but can I specify a user role instead of all users?
2. if I want to connect CONTACTS with DEALS, then do I just change post_type="posts" to post_type="deals" on the TO side?