You can use the attributes in V2RoomSearchCriteria to set the search criteria. For free-text search on the room name, just use the query attribute. You'd then want to verify that the search results are not empty before extracting the room attributes.

V2RoomSearchCriteria criteria = new V2RoomSearchCriteria().query("Deal Room 123");
V3RoomSearchResults results = bdk.streams().searchRooms(criteria);
if (results.getCount() >= 1) {
  String roomId = results.getRooms().get(0).getRoomSystemInfo().getId();
  bdk.streams().addMemberToRoom(someUserId, roomId);
}

You can also have a look at the corresponding REST endpoint docs for other attributes.
https://developers.symphony.com/restapi/reference/search-rooms-v3