It's true: the roadmap and the GOP budget are two different things. The GOP budget will be aspirational, and create 10-year picture of what federal deficits will look like if their policies were enacted. Ryan's roadmap, by contrast, is a bill (a series of GOP policies) that, if enacted, would create actual changes to the federal balance sheet. The GOP could use his legislation as a guideline for their own alternative budget, or they could use other policy ideas.
But Ryan's roadmap is an example of how Republican ideas could be implemented to lower deficits in the long term--and it's the only comprehensive plan out there. A snapshot of what the GOP would likely do to eliminate deficits if they returned to power.