There are a few ways to figure out if someone else is a Roblox Staff member or Admin.
One way to tell if someone is staff or not is to check the badges on their profile. All Roblox staff members will have the Roblox Admin badge located in their badge list. If they do not have this badge and are claiming to be staff, please be sure to let us know by using the Report Abuse links on their profile. The badge looks like this:
There is also a way to determine who works for Roblox while inside of games. When in-game, the leaderboard in the upper-right corner will list all players currently playing. Roblox staff will be indicated by a tilted square icon that looks like the one below:
For more information on this, check out this article on what various leaderboard icons mean and look like.
To find a list of Roblox Admins all you need to do is visit the Roblox admin group. While you can find a link to this on all admin profiles, you can also go there directly by clicking here.
It is also important to note that Roblox administrators will never ask you for your password. If anyone asks for your password or claims to be Roblox staff but does not have the Admin badge, please report them using the Report Abuse links located around the site.