Here in Jasper National Park, You could ride the paved trail around Lake Annette, and also the paved back road from Old Fort Point to Lac Beauvert. If you can manage hills on roller blades, you could go down the Old Fort Point road. The road to Marmot Basin would be another option. There are also the road at Lake Edith (but portions are rough) and the Pyramid Lake Road (but there is a fair bit of traffic on this one).
With the Legacy Trail, just be aware of the electric mats. I don't think you'd have any issue with rollerblades, as you'd be insulated by the blades. You'd just need to ensure that there's only plastic/rubber touching the ground, not anything metallic.
And even though you are going on paved trails, carry bearspray. You could encounter wildlife on any of those trails/roads - and going fast and fairly quietly on rollerblades, you're more likely to surprise wildlife.