Trello is great for a lot of things, but product roadmap management is not one of them. 

Building a roadmap with Trello takes a lot of work, and creates a huge amount of maintenance overhead. Loopliz, on the other hand, makes roadmap generation automatic. The roadmap is created from feature requests submitted by your users. As soon as you mark a feature as "Planned", "In-Progress", or "Done", it will automatically appear on your product roadmap. 

Here's an example roadmap: