I can confirm that there's no sign of an Isaac ROD(D)IS(S) marrying a Susannah on the Northamptonshire Marriage Index (1700-1837).
This surname also seems to have the variants RADISH, RADHOUSE and RODHOUSE (these have also been checked on the NMI) and are concentrated in the adjacent villages of Weedon Bec, Flore and Heyford.
FreeREG has a burial for a Susannah RODDIS at Flore on 29 OCT 1788.
There does seem to be some connection between this family and St. Sepulchre at Northampton. In 1728 a Thomas RADISH "of Flour" (sic) married there, and I have come across several other later similar marriages.
Incidentally, how do you know Isaac's birth year and place?
Pennie