If you're tolerant to either one by itself there's no reason to be concerned, you can take your normal dosages. If you don't regularly use either of them I'd take half what you normally would with the Valium since I'm not sure if you could halve the patch. With buprenorphine there's a low risk for respiratory depression vs other opioid + benzo combos so it's pretty safe together, but it's best to take it slow anyway.