On the basis on info contained in our catalogue of parishes in Montreal, about 1838, there were only three parishes:
Cath.: Notre-dame de MOntréal
Anglican (I believe) - Christ Church - Garrisson (a military parish it seems)
I have checked the records of the above churches for the Feb 12, 1838 and 10 days before and 10 days after that date and did not find a baptism of any William Rowley (Rawley, Rolley).Nothing that comes close to that name.
If you wish to pursue your research, the Mormons have microfilms of the churches records.They can be obtained and viewed at any of the Family History Centers.