How do I get the corresponding row for a RowsetID?
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.