Who are you flying with? ITA?
If you are flying with one ticket they should check the bag all the way through PMO (therefore there would be no need to retrieve bags in Rome), however make sure that is the case at check in (check that the bag tag says FCO - PMO (both should be in the tag for the bag to go to PMO).
The walk doesn't take long, at most 20-25 minutes depending on the gate of arrival and departure, however the time is mostly determined by the lines at passport control, since you come from outside Schengen. That can vary depending on how many international flights arrive at the same time. If you are flying through with the same ticket (i.e. no need to retrieve luggage and re-check in) you should be ok with a 1.5h-2h layover. If you miss the connection because of a flight delay from Canada, they should be able to rebook you with the next available flight (if you fly ITA they have multiple flights).
The issue is if you fly to PMO using a low cost airline like Ryan Air, therefore on a separate ticket, in which case you need to claim baggage and check in again. In that case give yourself at least 3 hours.