A quick look at https://devforum.roblox.com/ shows that they are using SSO to manage their login, so the answer to your question is yes, there is definitely a way if you know what auth/SSO provider they are using.
Once you figure that part out, it is now a task of configuring it to work with the different auth/SSO options available for Discourse. See the Official Single-Sign-On for Discourse (sso) for a start, and search through the community for other SSO options.