Hi Peggy: I found a John TOBIN married 6/1/1834 to a Margaret ROACH; witnesses Alice Whelan and Anna Daly.
From St. Joseph's marriages, p. 82 (of 86)
I am a descendant of the ROACH family from IL and WI and a John TOBIN signed as a witness for my ggf James ROACH to become a citizen of USA; the papers are from Dane Cty, WI. Also a Maria TOBIN was a witness to the wedding of my great aunt, Bridget ROACH when she married Patrick C HIGGINS on 10/15/1867 in Madison, WI.
I have a few obits from IL for a Margaret TOBIN if you are interested. Do you have a year of her death?
I also came across other TOBIN data if you are interested.