How to Join a Group in Roblox?

How to Make and Join Groups – Roblox Support

Click on the Searchbar, located at the top of the page.
Enter a keyword (e.g. "Ninjas" if looking for a group about ninjas)
Choose to search in groups.

How do you Join a Group on Roblox Mobile?

Accessing Groups
To access groups through the Mobile App, do the following: Tap the More "..." button at the bottom of the screen. From here, tap Groups. Select the group you wish to view.

Is it Free to Join Groups on Roblox?

For the Roblox Wiki category, see Category:Groups. All players on Roblox can join up to 100 groups. Anyone can create a group, but creating a group costs 100 Robux.