Well you can always back your text messages up with smsimport and the import them on the new rom. This program saves text messages as an xml file so you can view them in any program that supports xml files. I have just tested this program in WM 6.1 RdZLyZs version 1.2 and it works. After importing the messages back to the phone, you just have to open outlook. When you open text messages, outlook will sort the received messages from the same person in one conversation. Then when you open the conversation, outlook will sort your sent messages and add them back to the conversation. The text messages will be just like they were on the old rom.
You can get the program
here or the direct file
here. The program is an exe file and will run directly on your phone.