do the leaves come a twiggy stem? if yes then it looks like a mountain ash/rown seedling. they make a nice small tree but not next to your rose.

If the leaves come direct from the centre at soil level it looks like 'silverweed' which has a pretty yellow flower. It is a native wildflower.

thanks seaburn, had another look, think it might be silverweed. Will move it just in case it turns out to be the mountain ash!!