If they were formatted for soft raid, they need to be partitioned as fd, Linux Self-Detecting RAID, not just vanilla 83 Linux or Linux Swap. Then you need to make an /etc/raidtab, there's a sample with raidtools... then run mkraid /dev/md0, check in /proc/mdstat and wait for the kid to parrallelize, then format it for whatever filesystem... ext3, ext2, xfs, etc... and then it should be one whopping mountable chunk with /dev/md0
I forgot the partition part of that last weekend

If you've done the rest it should get detected automagically if you just change the partition types (although the sizes have to stay the same).
Cheers,
Finegan