How to get list of possible vm role sizes using REST API

Hello All,

Is there is some way to get list of vm role sizes (extra small, small, A6, A7) using REST API. I need to show them on internal portal so end-user could create vm from our internal portal. Of course items should also include at least short description. Not sure if role sizes vary by region. If so I would like to retrieve only availble for this region.