Back in January, I wrote an article about how you could retrieve the site URL of an Office 365 Group.
Linked article: Get the site URL of an Office 365 Group via the Microsoft Graph
The way how I achieved it back then was via calling the drive end-point and parsing the site URL from the response.
While I was testing out something today on the Graph Explorer, I noticed a new SharePoint Group end-point (atm only available on the beta endpoint). This makes it even easier to get the webUrl.
Info: At this moment, I did not find any details yet about the API end-point in the beta documentation, but I am sure that it would not be for long until this is also covered.
The new API endpoint can be called as follows: https://graph.microsoft.com/v1.0/groups/<group-id>/sites/root
Here is a sample:
When you only need the webUrl, you just have to call it as follows: https://graph.microsoft.com/v1.0/groups/<group-id>/sites/root?$select=webUrl or https://graph.microsoft.com/v1.0/groups/<group-id>/sites/root/weburl
Update
Apparently, Mikael Svenson had already posted this on his blog: Microsoft Graph adds SharePoint endpoint for Groups in the beta branch.
10/05/2017
A client discovered today that the SharePoint API end-point was not available anymore. The article has been updated with the new API endpoint to use.