In our business model, Epics are themes that encompass a number of related stories and tasks. Many of these are on-going (ie. performance, usability, integration, etc) and don't really fit well with the idea of the Roadmap/Gantt chart. And those that are time-constrained will still span multiple sprints, interspersed with sprints focussed on other Epics. So the Roadmap currently represents Epics well, but that isn't necessarily too informative with on-going Epics.
What would be helpful to us would be for an alternative Roadmap to be more of a heatmap, indicating how much of each Epic will be addressed in the given timeframe. For example, if we had 5 Epics (each might have a color associated with it) and the November would be 70% blue for Epic1, 20% green for Epic2 and 10% yellow for Epic3. Q1 2019 might be 10% Epic1, 20% Epic2, and 70% Epic3. Perhaps Q2 2019 is 100% Epic4 (which would be represented the same way the Roadmap currently works - a solid Epic name/color) and then work continues in Epic 1, 2 and 3 in Q3 2019.
This kind of Roadmap would better indicate the focus of work for a given time period. Instead of seeing that Epic1, 2 and 3 go on indefinitely with Epic 4 starting and stopping in Q2, we can see that we are focussing on Epic1 in November and continuing work through Q1, we are focussing on Epic3 in Q1 2019, and we are also maintaining a constant level of work in Epic2 throughout those times. We can also see that all work on those Epics stops in Q2 and then resumes in Q3. This is all far more visually informative than the existing Roadmap.
Just an idea to consider...