The Rochester Public Library has added “Early Marriages in Rochester, Monroe Co. and Vicinity” to their online collection of books. It appears to have marriages between 1818 and 1850. It is a typed collection of marriages from early church and newspaper records. This collection was compiled by Myrte Rice Haynes and Mary T. Douglas.
There aren’t any references in this collection of marriages to indicate where they came from. Some of the records probably came from the First Presbyterian Church of Rochester. There is a book in the Rochester Public Library that contains not only marriages but also admissions, baptisms, and deaths from 1815 to 1915 (see RPL #Rfr285.1 R676f).
Some of the marriage records came from St. Luke’s Episcopal Church. Rochester Genealogical Society has both a transcription of records from 1817 to 1850 online as this PDF file. RGS also has images of the original records online for 1817 – 1961 (see this web page for links).
Some of the early marriage records also came from old Rochester newspapers. I have also extracted old newspapers records from 1818 – 1830. See the Vital Records page on GenWeb of Monroe County. I noticed an error in one marriage record that was caused by an incorrect listing in the original newspaper. This book has “Acer, Henry to Polly Holden Dec. 15, 1818.” The abbreviation “inst.” is short for “instant” which in turn means “this month.” That marriage was listed in the Rochester Telegraph dated Dec. 15th 1818. News didn’t travel that fast in those days. It was still traveling by horse. Besides a second marriage entry in that issue of the newspaper says that a person was married on “the 16th inst.” Henry and Polly couldn’t have married on Dec. 15th. I suspected that they were married instead on Nov. 15th. Then I checked on FamilySearch Family Tree and the marriage listed for Henry “Acker” and Polly Holden says that they married on Sept. 15, 1818 (but no reference).
Use this book of marriage records as a starting point to find better references.