Rosetta 2 installation on M1 MBP fails
Don't know about the error message but the command also reports Install of Rosetta 2 finished successfully. So to check whether Rosetta actually got installed

Install an &quot;old&quot; application not recompiled for M1 yet (if you don't have one, any free application from the Store which hasn't been updated since May 2020 will do)
Run it to see if it works.

You can then also check in Activity Monitor by enabling the &quot;Architecture&quot; column there. If any process shows as&quot;Intel&quot;, Rosetta is installed