Roast squash: cut in 2 and remove seeds. Cut into 1 1/2 inch thick slices and toss with olive oil, a sprinkle of salt and 1/2 teaspoon rosemary. Roast slices in the top third of a 425F pre-heated oven for about 15-20 minutes, or until tender. Cool and cut into 1-inch pieces.
Whisk the beer, mustard, vinegar, olive oil, honey, and salt together.
Toss the squash with 1/3 of the vinaigrette in a bowl and let it rest for a 1-2 minutes. Add and mix the celery, onions, walnuts, raisins and 1/3 more of the vinaigrette. Toss again. The squash should absorb all the vinaigrette. Toss in the remaining vinaigrette gently and add more salt if needed. Let the salad rest 5-10 minutes before serving.