replacing exhaust vents

We have a berm house with only windows in the front, so we had solatubes and add-on exhaust vents installed for the back rooms, when we got a new roof (metal).
It looks like many mistakes were made with the install within the attic space and there is a mold problem on the OSB material.
We want to have the metal roofing and OSB replaced in back of house, and old vents replaced with a higher quality product.
Is this doable without horizontal cuts to the metal roofing?
And can exhaust vents such as these be used on a metal roof?
(http://www.luxurymetals.com/roofcaps.html#anchor_351)

We have soffit vents along front and back of house.
For the exhaust fans in the back rooms, we always open a front window when we turn them on. It's a small house.
The current vents didn't have a connector to attach the ducting to, so the ducting fell out eventually, and the ducting wasn't insulated.

How bad is the mold on the OSB and how long ago were the previous modifications (i.e. venting and new roof) done?

the mold is localized around ducting that came off

In that case, some topical treatment of the mold on the plywood is probably all that is required along with proper hook up to the exterior. You cannot nor should you dump any moisture into a vented attic. Fan vents should always go through the roof or home to the exterior and dumping at the soffit does not count.

The worst mold extends about 3' from the vent at the bathroom vent, a few others are not quite as bad. Looks like mold is probably on the roof side of OSB as well.
The metal roof was installed about 7 years ago along with the solatubes and ventilation add-ons.

First thing to do would be to remove the source of moisture. Treat the plywood and check the moisture content at that point.

If its 7 years in the making, the OSB could be shot.