The Rat-Pac trail requires a fair amount of an uphill climbing, but well worth it when you get to the downhill. It is a 12 mile loop with a fair amount of technical riding. The upper area was a bit overgrown, and had some downed trees, but the lower area was in great condition. Going late in the season, it was fairly cool and damp on the ride, but mid-summer the trail can get pretty dusty. Some of the ladder work was out when we went their in October - hoping to help get that all back up and running.
I live in Seattle, but grew up and still have family in Yakima. Roslyn has become the perfect middle ground to meet and mountain bike. Not only is the town amazing, but the trail system above the Roslyn is well maintained, fast and flowy. If in the area, take the Salmon la sac exit head up the hill following the roundabout and signs towards Roslyn. Spot at the local bike shop - the Ride Roslyn NW Bicycle Improvement Inc. - Super knowledgable staff and a great all around shop (can rent bikes there as well). Navigating to the trial head is well mapped out on Evergreen https://www.evergreenmtb.org/trails/rat-pac.