Let $G$ be a connected, simplyconnected complex semisimple Lie group with Lie algebra $\frak{g}$. Fix a maximal torus $T\subseteq G$, and let $$\frak{g}=\frak{t}\oplus\bigoplus_{\alpha\in\Delta}\frak{g}_{\alpha}$$ be the corresponding decomposition into weight spaces. Given a nonzero root vector $e_{\alpha}\in\frak{g}_{\alpha}$, is there a nice way to describe those root vectors lying in the nilpotent $G$orbit of $e_{\alpha}$? This is possible in the context of several examples, but is there a more exampleindependent description?

If $\alpha$ is a long root (e.g. if $\mathfrak g$ is simplylaced), then $e_\alpha$ is in the $G$orbit of the high weight vectors. Projectively, its orbit looks like $G/P_\Theta$ where $P_\theta$ is the parabolic using those simple roots that are perpendicular to the highest root. But you asked for the root vectors, not all the vectors. Then the answer is that you get all the root vectors for roots of the same length as $\alpha$. 

