The actual wording seems to vary slightly from one hotel chain to another but all of the ones I've checked refer to bed and breakfast rates (i.e. not 'room only'). These are examples from the Tesco website:
"Only valid on the Ramada Jarvis Flexible Bed and Breakfast rate"
"Tokens valid on Leisure Break B&B and Leisure Weekend Break B&B rates only" (Best Western)
"Only valid on Hilton Hotels' Best Available Bed & Breakfast rates"
"Only valid on Novotel Hotels' Bed and Breakfast rates"
To check the rules for the hotel group you're considering staying with, hover your cursor over 'Hotel breaks' here
http://www.tesco.com/clubcard/deals/
and select the relevant group. On the next screen, click 'More'
Chris