Looks like great new growth to me!

Thanks!

i haven't encountered a sucker in person yet and am still learning (as evidenced by not having buried the bud union while living in zone 6 hahah, welp I'll take care of it before winter haha)

Kali

Anything that grows from below the graft/bud union will be the root stock. I'm so used to own root roses I have a hard time knowing the bud union.

Looks like a nice basal cane, not a sucker. Basal canes emerging are like a new baby born into your family. They are the future of a rose bush.

Your bud union can be protected over winter with a nice heap of mulch. Very often, as time progresses over a few years, a bud union will sink into the ground as the bush settles in. By doing this the bush helps protect itself. Watch your bush and see if this happens and see if I'm not right!

Moses

Thanks Moses!! As always I appreciate the advice :)