Bring a large pot of lightly salted water to boiling. Carefully remove 1 cup of the boiling water and pour over sun-dried tomatoes in a medium bowl. Let stand for at least 5 minutes while making sauce. Add pasta to remaining water; cook 8 minutes, or as per package directions. Add artichoke hearts for the last 4 minutes. Drain and set aside.
Meanwhile, melt butter in a medium saucepan over medium heat. Sprinkle with flour and cook, whisking, for 1 minute. Pour in milk, oregano, salt and pepper. Bring to a simmer. Cook, whisking, 3 minutes.
Remove from heat and whisk in both cheeses. Drain and chop sun-dried tomatoes and stir into cheese sauce along with roasted peppers. Combine sauce with pasta-artichoke mixture and serve.