I don't see the Reds paying Jack Hanahan $1MM to play in AAA while paying Rolen a few million as well. But if Rolen signs, the Reds look like this:
C Hanigan (R)
1B Votto (L)
2B Phillips (R)
SS Cozart (R)
3B Frazier (R)
RF Bruce (L)
CF Choo (L)
LF Ludwick (R)
C Mesoraco (R)
OF Heisey (R)
IF Donald (R) - only backup SS on the 40 man
3B Rolen (R) - IF SIGNED
That leaves one bench spot and no lefties on the bench. The options are Hannahan, Paul and Henry Rodriguez. So, do you send down the guy you just signed to backup 3B and whose primary asset is his glove or do you send down the OF who "earned" a spot in limited time last year.
Personally, if they signed Rolen, I'd still carry Hannahan and send down Paul. Firstly, Paul and Hannahan are basically the same hitter; Paul just had a small sample BABIP blip in 2012. So the difference between them is glove value and flexibility.
Because Frazier can play a credible OF, I think carrying Hannahan wins on two fronts. Firstly, he's a step up defensively from Rolen too at this point. So he still makes sense as late inning sub. Paul is an average OF defensively and a step down from Heisey. Having Hannhan lets you keep him available on the bench while starting Rolen and given Dusty the option to use an all RH OF against a really tough lefty. Frazier is also free to play 1B if needed. He'd still be the primary 3B, but it gives you more options.
All things considered, given that its not my money, I'd take Rolen over Paul in a heartbeat, knowing that the on field difference is less significant than the value of having Rolen in the clubhouse. However, I'm not sure if Paul has an option. If he does, problem solved. If not, he may not clear waivers and that would leave the 40 man light on OF.