I am uncertain about Wilson vs. Roosevelt--that would depend on
how Roosevelt won the GOP nomination. If somehow Taft peacefully yielded the nomination to him, TR would certainly have a good chance of winning in November. But if TR gets the nomination only after a bitter convention fight (which is more likely) I think a lot of Taft supporters will refuse to vote for him unless he is very conciliatory, drops "radical" ideas like recall of judicial decisions, and assures pro-Taft politicians that he will not be vindictive in patronage appointments. And it will be hard for him to do this--it will make him look like a hypocrite after all the things he said during the nomination campaign.
I am much more confident that Wilson would beat Taft one-on-one. After all, the Democrats won control of the House of Representatives in 1910
before the Taft-TR split, largely because Taft was so unpopular. Indeed, much of the pressure in 1911 for TR to run came from Republicans who believed that he could defeat the Democrats in 1912 and Taft could not. But
The Nation indicated the problem with that in its January 11, 1912 issue:
"Taft 'cannot be elected.' This feeling is undoubtedly the true reason why many Republicans have faintly hoped that he would withdraw from the field. But as he has now definitely and even defiantly refused to withdraw, the real question before the party is: 'If Taft cannot be elected, can any Republican?' More specifically, the question is whether any Republican can be elected over Taft's dead body. It is confidently said that Roosevelt could be elected, but could he? Could he, that is, if he first had to go out and make open war upon Taft, with all the imputations of false friendship and desperate ambitions upon his head, with his party torn asunder in the process, and with countless Republican enemies eager to pay off old spites? Under those circumstances, it would not be a cool judgment that maintained he could win."
https://books.google.com/books?id=jWE5AQAAMAAJ&pg=PA27