A project roadmap provides a high level overview of your project planning as well as your project goals within a certain time horizon. This depends on your project and can vary from a couple of months up to several years. It lays out your strategic vision and enables you to keep everyone aligned and focused on what's really important.
Prioritize what tasks and project should make it to your roadmap. In most cases it makes sense to take the economic impact and strategic fit into account and rate these against the time you need to invest and the money you need to spend.
Cost (X) criteria
Value (Y) criteria
Bubble (R) criteria