@Frederica
You can control your RokuTV volume using the official Roku Remote App available from the Play/Apple stores that you download to a mobile device (phone/tablet). You can then control the TV from another room.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, 4802, 4850, Premiere+ 3921, Express 4k+ 3941, Streambar 9102