Rocket.Chat/packages/rocketchat-authorization/server/models/Subscriptions.js

RocketChat.models.Subscriptions.roleBaseQuery = function(userId, scope) {
	var query = { "u._id": userId }
	if (!_.isUndefined(scope)) {
		query.rid = scope;
	}
	return query;
}

RocketChat.models.Subscriptions.findUsersInRoles = function(roles, scope, options) {
	roles = [].concat(roles);

	var query = {
		roles: { $in: roles }
	}

	if (scope) {
		query.rid = scope;
	}

	subscriptions = this.find(query).fetch();

	users = _.compact(_.map(subscriptions, function(subscription) {
		if ('undefined' !== typeof subscription.u && 'undefined' !== typeof subscription.u._id)
			return subscription.u._id
	}));

	return RocketChat.models.Users.find({ _id: { $in: users } }, options);
}