Between Roosevelt NP and Glacier NP - highly recommend two side trips. First, Little Bighorn Battlefield National Monument. If you are at all familiar with the story, and everyone should be, this is a really cool experience and its never crowded. Doesn't take all day. Can be done in 2-3 hours, and you get to drive the whole battlefield and stop at key battle stations where there are markers explaining what took place at that location. If you're going, read up on the battle first. It will make actually being there much more special. Second, drive the Beartooth Highway. Being able to drive to 11,000 is so convenient. The mountain views are stunning. It's not directly between the two NPs and will take you through the north edge of Yellowstone (where it will be super crazy tourist busy in the summer), but still worth it.
Glacier NP - Going to the Sun Road is essential. Rasputin prefers the west to east drive.
Banff - Don't just go to Lake Louise and take your standard photo of the lake like a lazy tourist. Get there very early. You won't get to Moraine Lake if you're not there by 6AM. Too busy. Lake Louise will fill up fast too. Bring your boots, lots of water and a pocket full of cash, and hike up to Plain of Six Glaciers Tea House. There is no more accessible way to immerse yourself in the Canadian Rockies, away from the crowds at Lake Louise, than hiking to the tea house (takes 2-3 hours one way depending on your fitness, so round trip its 4-6 hours) and treating yourself to a large slice of chocolate cake and tea. Breathtaking scenery. If you're staying in Banff for a bit, the Rasputins favorite hidden gem of a hike is Stanley Glacier hike in nearby Kootenay NP. You will be pretty much all alone for a day in the mountains. The first hour is meh, but once you get up into the valley, and you can see the glacier ahead of you surrounded by sheer rock faces on both sides, you'll be awestruck. Pack a lunch and stop at the green oasis just below the glacier for a well deserved break. If you're not one for isolation don't do it though. It can be a bit intimidating being so far away from civilization and not many people are ever up there. And there may be grizzlies so bring bear spray.
Banff to Jasper - If you're doing the drive, you'll be on the Icefield Parkway. It's an event all on it's own. Take the time to stop at Peyto Lake. It will be packed with tourists because they all have to check that box and get that pic, but it's still worth it. When the parkway takes you close to one of the rivers, stop and get out. Take your shoes and socks off and the whole family can go stand in the creek and see who can last the longest in that glacier runoff. So damn cold! You won't last a minute. You should also consider doing the Parker Ridge hike. The first hour and a bit is nothing but boring switchbacks (but great cardio) but once you get up top you'll feel like you're in Lord of The Rings. The landscape is very reminiscent of New Zealand. From the top of the hike you can see the Saskatchewan glacier. Worth the effort. Finally, sign up for the Athabasca Glacier tour. Very touristy but worth it.
Could go on all day but you get the gist.