neither name is manx - Bawden as a family name came in from Cornwall (IIRC) with the mining mid 19th century.
Rossiter I have no record.

There would be very few, if any, baptisms at St Johns pre mid 19th century as it was a chapel of ease to St Peter's in Peel (kk german) (I have researched German PRegs pre 1765 and couldn't recall one ref to a baptism there though there were a few marriages - what sources do you have for your Manx background