Kosher food in the Canadian Rockies is almost non-existent.  If you keep kosher, the most practical thing to do is to stay in self-catering accommodation and prepare your own food.  

If you're interested in a group tour, Kosher Expeditions  does a group tour to the Canadian Rockies (as of 2010). Review.

If your trip is going to include a Sabbath during which you will not drive, your best bet is to stay in Banff townsite.  Lovely as Lake Louise is, it is a small village that is too far away from amenities to be convenient for you. 

Banff is a larger town with museums and attractions and nearby walking trails that can keep you meaningfully occupied on the Sabbath.  Banff's self-catering accommodations include Douglas Fir Resort, Hidden Ridge Resort and Tunnel Mountain Chalets.  

If you want to purchase kosher meats and dairy products, there are none in Banff and Canmore.  The closest source is CalgaryHaifa Deli at 3109 Palliser Drive SW, Calgary has a wide selection of frozen meat (beef, etc.).  The Safeway supermarket chain in Calgary has a much more limited selection of kosher food -- dairy products and frozen chicken.  The Calgary Jewish Community council has a webpage on kosher symbols that you may see on packaged foods in Canada.

If you were landing at Calgary Airport, you would need to shop for meat and dairy products in Calgary before continuing to Banff.  Since Calgary Airport is in the northeast quadrant of the city and Haifa Deli is in the southwest quadrant and quite far out of your way if you're bound for Banff, another Calgary store that may be of interest is Sunrise Spices & Halal Meat.  It is located at 4818 Westwinds Drive NE, which is considerably closer to the airport than Haifa Deli. 

Banff has two supermarkets, Nesters Market and Safeway, and the nearby town of Canmore has a large Sobeys supermarket.  There you can find fresh fruit and vegetables.  

Some of the restaurants on the Inside Banff : Vegetarian Dining page here at TripAdvisor may be acceptable to you.     

While the Fairmont Banff Springs Hotel does not have a kosher kitchen, it can order kosher meals from a company in Calgary, provided it has at least 48 hours notice.

Upon request, the Fairmont Jasper Park Lodger and the Fairmont Banff Springs provided a microwave at no charge. Both hotels had small refrigerators, which stored a week's worth of food. The Fairmont in Jasper uses real keys; the Fairmont in Banff uses electronic ones, but graciously offered to have a staff member open the room on Shobbos at any time. The Fairmont also allowed  lighting candles in the hotel room. The Safeway in Banff has no kosher bread or rolls, but there was breakfast cereal with OK and other hashgachot; Philadelphia cream cheese under MK (Montreal), Heinz Ketchup (COR) and Safeway Ketchup (OU), Annette's brand cookies and cakes (COR), pretzels (OU), and of course fruits and vegetables. So: bring your own food but in an emergency you can eat a lot of cereal. For those with Celiac disease, they also carried Ener-G brand gluten free bread (Chof K) and a brand of gluten free cookies (3 flavors, OU).