Yes Walmart stores do sell Rosemary and when you look for Rosemary at Walmart the Rosemary would be in the produce section.
If you can't find the Rosemary you can ask an associate in Walmart where it is.
I've seen Rosemary for sale at Walmart here in the produce section.
Walmart also sells Rosemary oil which would be in the medicine section of Walmart or the health and beauty section of Walmart.
So to find Rosemary oil in Walmart go towards the health and beauty section of Walmart and you should find it there.
It's where the Rosemary oil is here and the Rosemary leafs are in the produce section.