WP Query results showing posts outside of category ID

category_ID is not a valid key for WP_Query. cat would be available instead, if you want to query a category:

Example:

$args = array(
    'numberposts' => -1,
    'post_type'   => 'rooms',
    'cat'         => 8,
);

$the_query = new WP_Query( $args );

If your category is not actually the taxonnomy category but a custom taxonomy, this would be another way to query it:

$args = array(
    'numberposts' => -1,
    'post_type'   => 'rooms',
    'tax_query' => array(
        array(
            'taxonomy' => 'your-category-taxonomy',
            'terms'    => 8,
        ),
    ),
);

$the_query = new WP_Query( $args );

Hope this helps.