Is there any way to set up BOINC so that certain projects download more WUs faster than others? I have BOINC set up running all of the projects, but hoped to establish a priority gradient so that Rosetta@Home downloads and finishes more WUs than the other projects. Any ideas?

Have you visited "Project Preferences"? Those are project-specific pages. You can find them if you visit a project site, login and go to "Your account".

Under the Project Preferences there's also the "Resource share" setting. The page looks somewhat like that:
http://boinc.berkeley.edu/w/images/4/41/Project_prefs.jpg

Set low resource share for a project that you want to be favoured less. And higher value for a project you prefer. Stock value is 100, but you could set for example 30 for one project and 150 for another.

Then force update for those projects on the local host and the new information of their resource share will be updated. It will take some time until the situation will take a new direction. Those resource share values don't reflect directly how the resource share will really be between different projects. Those settings are more like "a wish".

I know that, but doesn't that simply demarcate the percentage of processing power to be delegated to a specific task? I was inquiring as to number of projects downloaded and processing order.

so that Rosetta@Home downloads and finishes more WUs than the other projects.

Well, from that I understood the most important thing would be Rosetta finishing plenty of work. Weight on the word "finishes". Donwload speed or amount of stored tasks woudn't even be so important, as long as there was enough downloaded tasks - at all times - ready for processing.

You would achieve that situation where Rosetta would finish more work than other projects (or better to say: more work than now), by setting a proportionally much bigger value for it on the "Resource share". Scheduler would do the job.

I found an old thread with some info (maybe useful):
https://boinc.bakerlab.org/rosetta/forum_thread.php?id=5465

I found an old thread with some info (maybe useful):
https://boinc.bakerlab.org/rosetta/forum_thread.php?id=5465

I found the Information in this posting and in the one which is being referred to very useful, although to some point things were clear to me even before.
Many thanks for explaining it publicly :-)

However, I am still wondering about following behaviour of BOINC:
Among some other projects, I have Atlas@Home and NFS@Home with ressource share 300 each. So I would expect that say 2 WUs of the one and 2 WUs of the other are being crunched at the same time. But, in reality, they change completely after some time: 4 WUs from Atlas are being crunched for say 1 hour, then they are stopped and 4 WUs from NFS are being crunched for say the next hour; and then vice-versa.
Can I make some changes in the settings to the effect that for example 2 WUs of Atlas and 2 WUs of NFS are being computed simultaneously?