You have regular users that use your website/services, they can login to mainsite1, then you have developers, that can not login to mainsite1, but can login to developercenter1. Do you:
1) Store every type of users into 1 large USER table then assign different roles?
or
2) Create a completely separate table just for developers, since they are both completely different users using two different sites?
It's probably appropriate to centralise the logins, then add roles, and then link special properties for each group through a related table.
So yes, I'd assign roles, and keep login centralised (this means it can be one codebase to do the login, which is good).