Setting score to moving variable
Solution 1:
To set the "RoomID" score equal to "Rooms" you would do this:
scoreboard players operation <player> RoomID = <player> Rooms
with <player>
being a player either by username, target selector or *
, to select all players.
To add one to the "Rooms" score you would do this:
scoreboard players add <player> Rooms 1
Again, <player>
being a player either by username, target selector or *
, to select all players.