Many plants shed their older leaves as they grow, and for many plants those are the lower leaves.* I've found that many varieties of roses will lose their lower leaves, that's why many folks plant other flowering plants in front of them, to cover the 'bare knees'.* Many vines will do the same as did my moon flowers when I grew them.* Generally, once leaves turn yellow, they don't turn green again.* I would remove them and any that are on the ground, especially with the roses.
Newt
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.