As a developer working with OAuth, there are many of Open Cloud endpoints that would be useful if they accepted OAuth authentication.
Data and memory stores
My app allows users to manage their experiences and places, and it would be helpful to allow them to edit their data stores as well. Users are currently required to input an API key to use the data store features.
Toolbox-service
These endpoints do not require any authentication, but do allow higher rate limits while authenticated. This request was also mentioned here.
Developer Products
Game Passes
If Roblox were able to address this, it would go a long way towards the goal of offering robust OAuth2 capabilities. The use-cases for all of these are featured on the app I am working on which is publicly available on Android and iOS.