Based on my experience with roofers is all they want to to is replace the shingles and move on. Additional soffits can be added, but the might consider that a job for a carpenter who may not want to do a small job or coordinate his work with the roofers. I also have a small ridge line vents on a hip roof with a thermostae controled roof mounted ventilator. The ventilator keeps the attic 10-20 degrees cooler that what I had without it. But you are right, you probably need more soffit vents to draw the air up. There are also different size ventilators. Depends on the size of your attic as to what size you need. Larger is not necessarly better. The roofers I consulted with didn't know anything about this; most didn't speek much English either. My self research also indicated that the ventilator shouldn't be installed with the ridge vents. The roofers disagreed and I ended up with both. Appears to work well with both. The important thing is to get the hot air out and increase circulation.
Re: roof mounted power attic ventilator
I also have a small ridge line vents on a hip roof with a thermostae controled roof mounted ventilator. The ventilator keeps the attic 10-20 degrees cooler that what I had without it. But you are right, you probably need more soffit vents to draw the air up. There are also different size ventilators. Depends on the size of your attic as to what size you need. Larger is not necessarly better. The roofers I consulted with didn't know anything about this; most didn't speek much English either. My self research also indicated that the ventilator shouldn't be installed with the ridge vents. The roofers disagreed and I ended up with both. Appears to work well with both. The important thing is to get the hot air out and increase circulation.