I kind of like Rolen the best of the bunch. Even in his last few down years his BB:K rate has been solid, so he's still a smart patient hitter. He should post the best batting average of the bunch, though Lowell could press him. Coming off a miserable 3-18 week, but he has 2 HR's already this season, so it may not be out of the realm of possibility he pops 20. I like the combination of the Jays lineup/Rolen's spot in it the best as well. You could also consider riding the streakiness of Reynolds, and play the hot hand approach. Good luck.
I would rule out Rolen and Giambi first off. Out of the remaining I like Lowel if he is healthy and producing like usual. He should be the best for your average as well over Reynolds and Jacobs.