Sounds like you are doing a good job of researching all the local sites I am aware of. But, I am sure someone will respond who knows more. Here is something I have run into: Could the surname be misspelled possibly in the Rochester marriage database? Or if a husband died before the wife, could the wife have re-married and now have a different surname to search on? Another thought: are you using the familysearch.org web site to search? It has been very helpful to me in the past. Lots of great data there. I presume you have also checked the census records to narrow down the time period in which a spouse has died. Just a few thoughts.