Unofficial roblox:// protocol documentation

• To join a game:

                    roblox://experiences/start?placeId=<placeId>
                

• To join a specific game instance:

                    roblox://experiences/start?placeId=<placeId>&gameInstanceId=<jobId>
                

• To join a private server:

                    roblox://experiences/start?placeId=<placeId>&linkCode=<privateServerLinkCode>
                

• To follow a user into game:

                    roblox://experiences/start?userId=<userId>