Pretty sure Angelina is the only S. rupestre hardy in our area. The Lemon Ball variety is sold here as an annual, but will not winter over

Hmm, so Santa Rosa is selling this as a zone 3 hardy plant.

Lemon Ball is not hardy at all. I was growing both Angelina and Lemon ball last year. Angelina did very well and survived the past brutal winter with no problem at all.
Lemon Ball didn't survive - in fact, it didn't even make it to the winter, it turned into gooey mush after the first hard freeze in late fall and was finished.
In my opinion, Lemon Ball is an annual, expect it to die after the first decent frost.

Santa Rosa (a nursery I am not familiar with) is wrong.

I believe Santa Rosa Gardens is the second largest perennial mail order source in the US.

I sent them an email to ask why they have it listed to zone 3.

They are all over the map on this one. I have seen 3-7 right up to zones 6-9. I can predict their response will be "We were using the zonal rating given by our supplier."
I think it has happened to every nursery that simply believes the info given is correct without checking first. Some breeders are so keen to get their plant to market before fully trialing it. We have seen it with Echinaceas,Coreopsis and Heucheras in particular. We northern gardeners need to be really careful in our selections.

What is the first and largest perennial mail order source in the US?

I planted Angelina this Summer--I'm glad to hear it's tough!

Santa Rosa changed the listing to zone 6 min after I contacted them. Good move on their part.

I live in Seattle, my lemon ball grew exponentially from when i planted it last march until the first frost in winter..turned to mush and died, however my angelina weathered through it with flying colors...i will treat it as an annual from now on

I'm in Zone 7B and I have several lemon ball sedum that come back every year. After the first hard freeze they turn to a slimey, goey, glob and it's easy to think they are dead. I cut them back to the ground to remove all the slime and once the temps start to climb they start to leaf out again. This past winter the temp went down to 9 degrees and 2 years ago it went down to zero with temps remaining below zero for several days... they still came back. Too much water is a sure fire way to kill these as they will develop root rot so if you are giving them excess water trying to revive them when you think the freeze got them then you may have killed them by doing so.