Here is list of players who might be added to the Twins 40 player roster this fall. I may have missed someone, but I don't think so. ( I did miss someone - see update below) Most of this years candidates were already added during the season.
2006 Draft - Tyler Robertson was eligible last year, I don't see much reason to think he is more likely to be taken in the rule 5 draft this year.
Here are the players eligible for the first time this year:
2007 Draft - Danny Rams, Angel Morales
2008 Draft - Carlos Gutierrez, Bruce Pugh
2007 FA - Oswaldo Arcia
There will be three roster spots open when the following players become free agents: Cuddyer, Kubel, Capps
A fourth spot will be opened if the Twins don't picky up Nathan's option.
There are two players currently on the 60 day DL who don't count toward the current 40 players but will have to be added: Casilla and Blackburn.
That leaves the Twins with one or two open roster spots and 5 or 6 candidates to be added to the roster. There are a number of players who might be taken off the roster and assigned to Rochester. They would need to pass through waivers first. Here is a list of more or less likely possibilities with a comment on each:
Manship - He was hurt this year and was not that good when he was healthy last year. He might pass through waivers.
Slama - See Manship
Dumatrait - He is a mediocre lefty. That is a reason both to let him go and to keep him.
Waldrop - Waldrop might be able to pass through waivers.
Rivera - The Twins are talking about finding an offense oriented catcher. That isn't Rivera, who is really a duplicate of Butera only not as good.
Nishioka - The Twins have Nishioka signed for 3 years. It is very doubtful any team is going to claim him on waivers and take on that contract.
Dinkelman - He passed through waivers once already this year. Its not hard to see him doing it again.
Repko - With Revere on the roster and able to back up Span, its not clear Repko fits as the Twins 4th outfielder any more. Pinch hitting skills might be a more important priority.
Twins waive one or more of the above players and add Gutierrez, Arcia and Morales to the roster.
Update 1: The Twins removed Tolbert, Rivera, Repko and Slama from the roster.
Update 2: Brett Jacobson who came from Baltimore in the Hardy trade is also eligible for the rule 5 draft this year. He seems like a likely addition to the roster.
Update 3(10/20/2011): Twins removed Dinkelman and Dumatrait from their roster