While coin roll searching, I, of course, come across Canadian pennies and nickles. My question is: Which ones do I need to consider keeping? (any particular years)
I'm guessing you mostly come across the George VI and Elizabeth II coins. For pennies, hold on to the 1949, 1955 and 1965 dates. For nickels hold on to the 1947 if there is a small dot next to the base of the 7 in the date, 1951, 1953, 1964 and 1965 years. These years all have scarce or rare varieties that are worth much more than regular examples even in circulated grades. You would still need to figure out the variety of course, but there are plenty of resources available to help you do so.
http://www.coinsandcanada.com/coins-prices.php Could help you out with different varieties and values