Vision basically is a goal you set for your organization, the product or even for yourself. A Vision Statement describes the desired future position of the company. There are three elements which constitute a vision on a broader level, the purpose, the picture, and the values.
The strategy is a system of achievable goals and visions which describes who the customers are, how the product fits into the current market, and how it will achieve business goals. In contrast to the product vision, which should have a lifetime of many years, a product strategy is typically seen to look at a horizon of months to a few years.
The roadmap describes what products and features will be built to realize the strategy and vision, who is responsible for building those product features, and, sometimes, an estimate of when those products and features will be released.