The doctors at Kaiser know that Roscoe has pulmonary hypertension, but the echocardiogram (ultrasound for his heart) doesn't show the level of detail needed to determine how severe it is. This is why they are transferring him to UCSF. UCSF Medical Center specializes in treating heart-related issues, so any child with a serious heart problem in the area would go there.
Depending on the severity, Roscoe's pulmonary hypertension may be treated with gases (oxygen, nitric oxide) or various medications (including viagra). In an extreme case, where the hypertension is coupled with pulmonary stenosis, there may be no treatment and the outlook would be grim. You can read more about pulmonary hypertension here and pulmonary stenosis here. Mainly I'm just trying to relay what I think I've heard from the doctors, coupled with some additional web searching.
Roscoe will arrive on Tuesday mid-day and will be checked in at UCSF. On Wednesday they'll insert a catheter that allows them to measure the pressure in the problematic blood vessel. Roscoe has experience with this, because the doctors have said the catheter will be alot like the PICC line he had a few months ago. Once the catheter is in, the doctors will iterate over several treatment methods and they'll be able to instantly measure whether Roscoe's blood vessels widen in response to the treatment.
Our prayer is that the doctors find at least one treatment that Roscoe responds to. Our secondary prayer is that the doctors find a treatment that can be administered in Roseville. Some of the treatments can only be administered at UCSF, so if those are the only successful treatment options then Roscoe will need to stay at UCSF for the duration of the treatments (which may be a month or more). We appreciate the prayers of everyone and we have no doubt that Roscoe has made it this far based on God's intervention. Please petition him to finish his work in Roscoe by resolving this hurdle on Roscoe's journey to be home with us.