How do I get the corresponding row for a RowsetID? We're faced with the following error when a query runs against a partitioned table with Read-Only file groups:


  The index "ix_my_index" for table "dbo.my_table" (RowsetId 72057600379912192) resides on a read-only filegroup ("MyFileGroup"), which cannot be modified


How would I identify which row the query is trying to modify from the RowsetID?

I know sysrowsets used to exist, but doesn't seem to in SQL Server 2012.
That looks like a partition_id to me, not "a row." You can start to get an idea of what values might be stored in that partition through the following:

SELECT partition_number
  FROM sys.partitions
  WHERE partition_id = 72057600379912192;


Then you'll have to look at the partition function / scheme to tell where the boundaries are for that specific partition.

I don't think sys.sysrowsets is going to tell you anything that sys.partitions won't. It's unfortunate that the product interchanges words like partition_id, hobt_id, and RowsetId so carelessly.