Rinse rice; drain. In a medium saucepan, combine rice, oil and water; bring to the boil. Reduce heat, cover and simmer for 30 minutes.
Meanwhile, in a large pot, cook onion, celery and carrots in margarine until vegetables are almost tender. Blend in flour, cook and stir for 2 minutes. Add stock and undrained rice, bring to the boil. Cook and stir until slightly thickened.
Stir in cream, rosemary and salt. Reduce heat and simmer, uncovered, about 20 minutes or until rice is tender.