"Tons" of bouldering is an overstatement in regards to Erie/Fidalgo. Goliath is fun, but limited in terms of intermediate routes. The harder routes are especially hard for a guy with a smaller wingspan. The Rosario wall you may be thinking of is Refridge wall, and while I have done a lot of traversing there, it gets boring for bouldering after a while, though I do climb there a lot. It's pretty wet however, and due to that, winters will ruin little routes that you had been workingon, as the rock tends to come off in chunks.
I know of one pretty interesting bouldering problem on the upper part of Erie, west of powerline that I don't think many people have been to. There are another couple of boulders on the road up to the top that could use some more exploring. And after years of hiking the area, I'm convinced that there are other spots waiting to be developed. But I'm not motivated enough to do it by myself. And all my bouldering buddies have moved.
And yes, I know that if I got in my car, I could find bouldering spots from here to Bellingham. But I already have enough hobbies that require driving in my car. And for that matter, I already have climbing partners if I want to drive an hour. I'm hoping to find people who either live here, or enjoy coming to Erie for some reason.