This thread should answer all your questions.
Note: A subdomain is really just a subdirectory with its URL displayed in a different way. In other words, and using one of your examples, you can reach a subdomain like this:
http://subdomain1.mysite.com/
or you can reach it this way:
http://www.mysite.com/subdomain1/
So you can setup your robots.txt just like it's done in that thread I gave you the link to.
Hope this helps.