Is this a typo?
sudo mdadm --assemble /dev/md1 /dev/sda2 /dev/sdb2
mount /dev/md0 /mnt/md1/ -o ro
When your assembled device cannot be mounted, it doesn't have a filesystem (swap?), the filesystem is damaged, or the filesystem isn't supported.
You can check if you've got the right partitions by executing
/dev/md1 should have the right size. You can check if the filesystem is supported by
can tell something about the filesystem on /dev/md1.
When everythink is allright here, apparently the filesystem is damaged. You could try to install xfsprogs, and then run
But this could cause further damage, so I recommend to first try to get your data back using a recovery tool like PhotoReq
(is also in the Ubuntu repository. Despite it's name it can recover *much more* than only pictures) Run PhotoRec on /dev/md1 (or whatever devicenode you used to assemble the array).
PhotoRec won't change the contents of the array.