Thanks for the good question / posited “what you said is unclear,” to me: I am happy to respond.
For every case I can think of, a truly circular (roundtrip) route relation (whether hiking, bicycle, equestrian…) should have the
roundtrip=yes tag upon it, and as if it is truly bidirectional (I don’t see why it wouldn’t be, but of course, I do have to say this), nothing else but the simple bidirectional route with that tag is required. True, there might be, say, something like a “very steep” portion or something which is appropriate in one direction, but not another, and then there would be a “longer, loop-around” portion which is appropriate in the other direction…and in that case, you’d use
backward role tags (depending on the direction of the underlying ways). How to do this is fairly well-documented and widely understood.
Then, there are the great majority of routes which are not
roundtrip=yes. These can be entered into OSM as either bidirectional or unidirectional. The “optimal” circumstance is when there are no “different” (based on the direction you are going along the route) ways in the route as elements: in that case, make the route bidirectional (only one relation, travel in both directions is allowed on each and every single way), there is no need for
backward role tags at all, and you are done with the route. It is simple, simply entered, and easily understandable (as able to be traversed in both directions). AND there is no reason to “double the data” by adding another route (for the other direction) with two unidirectional routes: why do so when there isn’t any need to? (You’ve entered a bidirectional route).
So to directly answer your question, no, for roundtrip routes, UNLESS there are different ways where only “in this direction along the route travel is allowed,” there isn’t any need to add
backward role tags. For non-roundtrip routes, these role tags are only required where there are ways that require “only in this direction travel.” Does that make sense / help? Again, I’m happy to continue to engage so you understand things, but this can be tricky until you “get it.” Looking at existing route relations (with role tags) can be helpful, too. (And I recommend the JOSM editor to do so, as it has an excellent relation editor dialog window that, at least for me, visually makes these concepts fairly clear).
Edit: All of this really does take practice. I would say it took me many months, even a year, to fully encompass the differences between various flavors of route relations and how the
backward tags are correctly applied, as well as the distinctions between unidirectional and bidirectional route relations. Please persevere: while some in OSM might feel a steep learning curve, it is well worth it once mastered.