It just means the Roses/flowers are blooming - the flowers have opened.

In this context it most likely means the roses bloomed a few days ago Another example: “Let’s go for a walk while the sun is out” The verbiage “is out” means “is presentable/visible”

Of course, to be out has another meaning. I guess it’s gay guys who open up and tell people they are gay

Welcome. 🙏🎶🌈

It is present perfect "Be" in present perfect is been The roses are out is simple present but in present perfect: the roses have been out.