Cook linguine according to package instructions in salted water till al dente. Strain and set aside.
Heat 1 tablespoon butter in a skillet and add sliced sausages. Cook on medium heat till light brown on both sides. Transfer them to a plate and set aside.
Add the remaining butter to the pan along with garlic. Saute the garlic for a minute or two till fragrant and add all purpose flour. Cook the flour for 1-2 minutes and add cajun spice and oregano. Mix well and then slowly add milk while continuously mixing to make sure there are no lumps. Simmer the sauce till it starts thickening up.
Add cream cheese and bell peppers and simmer for another 3-4 minutes till the cream cheese is combined and the bell peppers are slightly tender, but still crispy. Check for seasoning and add more salt if necessary.
Add back the sausages and cooked linguine and toss everything in the sauce. Top with chopped parsley and grated parmesan if using. Serve immediately!