Preheat oven to 180°C (approximately 350°F.)
Mix pork with oil and roast in oven about 40 minutes, occasionally brushing with juices and adding water if necessary.
Rinse potatoes well and cook with peel in salt water for about 30 minutes.
Peel carrots, cut into slices and fry in 1 tablespoon butter. Pour in about 75 ml (approximately 1/3 cup) water, salt and pepper, cover and cook for about 5 minutes. Add peas and cook uncovered for about 2 minutes.
Melt remaining butter in small saucepan, stir in flour, sauté briefly, and add cream. Stir mixture with whisk, bring to boil, season with salt, pepper and vinegar and simmer over low heat for 10 minutes, stirring occasionally.
Mix sauce with vegetables and season.
Cut roasted pork into slices and serve topped with vegetables, potatoes and parsley.