Look at the syntax in
screen [ -options ] [ cmd [ args ] ]
cmd is a command to run in the session. So, typing
screen SomeScript.sh would make it execute SomeScript.sh automatically, without going into screen and typing this.
If you're looking for a way to have screen execute some command(s) every time you start a new session, I do it by putting them in ~/.screen-start and putting something like this at the end of .bashrc:
if [ -n "$STY" ]; then
Since screen sets $STY to the screen session identifier, you can test for whether it's set to know if screen is running. And since screen starts a login shell when invoked without a specific command, it will execute .bashrc.
There is probably a better way; I stopped looking since this worked well for me.