To answer some of the questions:

No underpasses that I'm aware of, and certainly none that are accessible by bicycle, not many waterways in the area.

The safe route adds 5 miles to the trip, so a 10 mile ride each way for me. It's not terrible, and I'd certainly go that route if no other options were available, but I'd like to avoid it too.

North on either bridge while waiting for the lights to cycle is probably the best option, likely Barrington as it tends to have less traffic. The light is usually long enough that I can get from the light past the off-ramp, and I do see occasional bicycle traffic over that bridge.

Good thought on asking the LBS though; they're right next to the Roselle bridge, and so might be familiar with the issue. I'll stop in tonight, and see about the bicycle safety classes as well.

Thanks all for the advice!