We've used tons of different tools for creating roadmaps in the past: dedicated roadmap software, kanban boards, wiki tools, spreadsheets and design tools.
Some common problems with these tools are that they:
We were previously working on a product solving complex scheduling problems involving thousands of tasks and constraints when we realized that we had users (including ourselves) that were using our scheduler to create product roadmaps (and enjoyed it!). That's why we decided to create rmap.io.