You don't answer the incisive points I raised ... but I expect nothing more ... have a great day.
Obviously you have no idea of what winter road conditions can be like in BC, it is not just the Rockies that the OP will have to cross. Seeing as I live here, and the topic of road conditions is in our news every single day for months, I have much better knowledge about this than a casual visitor who happened to be lucky and get good road conditions. Someone needs a hobby better suited to them.
Spot on!
You don't answer the incisive points I raised ... but I expect nothing more ... have a great day.
What point (s) did you raise? That roads would be plowed? If that is it, then you really, really just don't have a clue. But I don't expect someone from a warm climate to understand, that is why those who live in the snowy areas give advice.
To the OP, there are hundreds of questions like yours on the other travel forum.
If you provided as many useful answers on Canada as I do, I would then expect you to be entitled to have a view. And no need to argue ad hominem ... it's such an ugly look. Do you really want to appear at the same low level as #11?

SNOW ? is not the only thing that causes road closures. Twice when i visited out thataway roads were close due to rockfalls. .found it daunting just driving on clear dry roads as they get very very steep in some places. The scenic view 's come at a price.
I think we need a reality check here ... whether you're driving to Whistler, Kamloops, Jasper, Lake Louise, Yoho, or Banff ... 90% of the likely driving for the OP would look pretty much like this. Even the drive from Lake Louise up to Moraine Lake is fairly straightforward.
And I have already agreed that the motor-home is not a good idea ... overnight temps in a van can be too low ... no argument there.

The road to Moraine Lake is shut until late May. So if you're suggesting they drive there in April, you really don't have much experience in the area. The lower section of the road is a xc ski trail until April, the upper section off limits due to major avalanche run outs.
As to Jasper - I would not suggest for folks to drive from Lake Louise to Jasper in the winter, let alone in an RV. Been along the parkway many times in the winter, and it's a whole different ball game. Not at all pleasure driving - no pullovers, no gas/stores/houses/hotels, no cell reception, very limited maintainance & patrols and not infrequent closures due to weather/avalanches/avalanche control. Full snow tires required. To get to Marmot, take the daily SunDogs shuttle from Calgary/Canmore/Banff.
As to the rest of the driving, I've done plenty of drives in the winter around the Rockies and inland BC and more often then not, conditions are not perfect. Even a skiff of snow in Kicking Horse Pass can hide lane lines, snow drifts/plow debris narrow the lanes and tractor trailers can blind you when they kick up snow/slush/ice. Plenty of white knuckle moments there.
M+S tires, minimum are required on inland BC highways - like snow tires, they must be specially requested, cost extra and are not always available. Also, note that in some places, you cannot pull over (even if it's actually plowed) - in Glacier NP, there are strict rules about where you can and can't pull over/park because they use live explosives to clear avalanches. And they don't always land in the right place or go off.
If you just want to ski in the Lake Louise/Banff area and the Whistler area, just fly between Vancouver and Calgary. Much less hassle and probably no more expensive by the time you factor in car rental, snow tires, accommodation on the way, gas etc. The drive from Calgary as far as Lake Louise is just fine barring a storm.
I give a huge amount of solid advice on the Canadian Rockies (and much else Canadian) year in and year out, and if I make an error (such as the Moraine Lake road closure), then I am very pleased to have it pointed out respectfully, as you have done.
But I don't appreciate personal attack from those who hardly ever make a genuine contribution on anything.
And I have already stated that I think the OP should get a sedan with proper tyres, and stay in hostels or budget motels. Anyway ... one of the secrets to successful travel is to pick the right season for each place.
The late spring driviing photo posted certainly portrays a pretty scene.
But then you will have late spring (really considered summer given the weather not up in the mountains) driving like this, I have also experienced heavy snowfall on the highway in late May.
http://www.castanet.net/edition/news-story-166191-1-.htm#166191
(link may not last long)