Just running this by you, Jane Roberts is as age 68 and with not finding a baptism for John, do you think John could be a Jones?
However, I did find a marriage of a John Roberts to Mary Ann Taylor, Wrexham 1839
http://www.rootschat.com/links/01tsr/Father John Roberts mason
Wit. John Roberts, Jane Evans
Collier on marriage, born Brymbo and Collier on census returns, birth 1821/1822
1851 Census, Brymbo John, Mary, Ed, Jane
http://www.rootschat.com/links/01tss/Jane Q1 Wrexham 1847 MMN Taylor