1880 census, Wisconsin, Waushara, Richford and Dakota twp
Roberts, William 62 Farmer NY UNK UNK J. F. 52 Wife GER GER GER Fred 19 Son WI Lydia 15 Dau WI Jessie 13 Dau WI Niellie 11 Dau WI May 11 Dau WI
1870 Census, Wisconsin, Fond du Lac, Ward 2
Roberts, William 53 Shoemaker NY J. F. 43 GER William 19 WI Amelia 18 WI Robert 16 WI Thomas 14 WI Edward 11 WI Fred 9 WI Alferd 7 WI Lydia 5 WI Jessie 3 WI May 1 WI Ellen 1 WI (May and Ellen were listed as twins)
1860 Census, Wisconisn, Calumet, Charlestown
Roberts, William 38 Shoemaker NY Joanna 35 Prussia William 9 WI Mary (Amelia) 7 WI Robert 6 WI Thomas 5 WI Edward 11/12 WI
I did a quick search of the 1850 census, but he was nowhere to be found in Wisconisn.It is possible that he wasn't in the state at that time.Regardless, this should give you a good start on this family.
I wish you the very best of luck with your continued research.