Add custom venue meta items by using the tribe_register_meta for individual items or tribe_register_meta_group for the group registration. See TEC (core plugin)/public/advanced-functions/meta.php for examples of group and individual registration

custom_venue_info.php

<?php

// add custom venue meta items
add_action('tribe_events_before_view','custom_venue_info');
function custom_venue_info(){
  global $post;
	// force this to run only on single event views
	if( is_single() && tribe_is_event( $post->ID ) ){
		$room = get_post_meta( $post->ID, '_VenueRoom', true );
		tribe_register_meta( 'tribe_venue_room', array(
			'label' => __( 'Room:', 'tribe-events-calendar' ),
			'meta_value' => $room,
			'group' => 'tribe_event_venue'
		) );
	}
}

// add the new custom meta into the template keys for custom templates on single event views
add_action( 'tribe_events_single_event_meta_template_keys', 'custom_meta_keys');
function custom_meta_keys( $keys ){
	$keys[] = 'tribe_venue_room';
  // any new meta items you create, add them here to be included in the template reset by single-event.php
	return $keys;
}