Pushing boundaries with new green roof plants

So last year I tried a few new species on green roofs and in my backyard.  After some research I thought a few could do quite well in lower Canada, upper USA. Here's what I found:

Rhodiola rosea

Did quite well on a rooftop and I am definitely incorporating this into future green roofs!

Rosularia sedoides

This was a backyard experiment, I wondered how it would with just moderate sun (3-4 hours).
It didn't make it to the spring.

Sempervivium arachnoideum "rubrum"

In full sun this could be quite lovely as an accent plant, I thought it had no chance of coming back this year but it did...in full-sun.

Erysimum pulchellum

Veronica liwanensis

The two above had a rough time from the very beginning with little water, despite ample (at least 5 hours) of sun. I'll keep both of these for sunny, ground level gardens.