Here's a couple places to start:

http://mlb.mlb.com/mlb/official_info/about_mlb/rules_regulations.jsp

https://en.wikipedia.org/wiki/Major_League_Baseball_rosters

https://en.wikipedia.org/wiki/Major_League_Baseball_transactions

http://www.brewcrewball.com/2009/1/4/703125/the-40-man-roster-how-does

Thanks Chief! Needed to read all 4 to completely understand the process. I think I've got it!

I'll pour over these too, at some point.

But it occurred to me to ask. How is Santana's post season suspension handled from a team perspective?

Does it have the same effect as someone not being able to play due to injury and thus being on the DL allows the team to replace that player with someone from the September call ups?

I believe anyone who has been on the 25 man roster prior to September 1st is eligible for the playoffs. This is one deciding factor in the waiver trade deadline being August 31st.

Suspended players are placed on the "restricted list" which don't count towards the 40-man roster.

I think he'd stay on the 40-man for the playoffs, though. He is just ineligible to be added to the playoff roster.