You will have to create a new room. Your data should still be in OneDrive. If you want to use the same room name, I would go online and rename the folder in your OneDrive to something else. Go into the People Hub on your phone and hit the + to create a new room. Re-invite people to the room. Go back online and move the data from the old room folder you renamed into the one just created. Everything will sync back up. I just did it 2 months ago.
EDIT-ADD: I must also add that if you had onenote notes, I had to move the note pages from one to the other. Just moving the onenote file may not work. I don't think it will sync up correctly. I maybe wrong, but it worked for me to just move the pages from the old to the new one created. It was a little bit of work but it I got it to work correctly again.