Combine lemon zest and juice from 1 lemon in a large bowl with the garlic, pepper, 3/4 tsp. salt, the oil, and roasted peppers.
Put juice from remaining lemon in another large bowl, half full of water. Pull off and discard outer leaves from 1 artichoke at a time, down to tender, pale centers. Cut off and discard thorny tips, trim stems, and drop into lemon water.
Slice 1 artichoke at a time paper-thin lengthwise, using a mandoline or knife, and stir as cut into pepper mixture. Let stand about 30 minutes.
Meanwhile, cook pasta as package directs in a large pot of salted boiling water. Drain pasta, saving 1 cup pasta water. Toss pasta with pepper mixture, then with parsley and 1/2 cup almonds. Mix in a little pasta water if needed for a looser texture. Serve with remaining almonds and season with salt to taste.