So far (to our knowledge, since we currently do not have alternate ways to circumvent the need of R-Tanks), at least 1 R-Tank is required for the setup at Colosseum, for the very first bombjump (a reserve-bombjump): http://puu.sh/mu5GH/b01646d59f.mp4
What happens in there is that the bomb is laid right before the reserves kick in, but the bomb-timer continues during the energy refill, while Samus stays in place, which results in a diagonal bombjump.
Edit: To be more precise, what happens in this setup is the following: As you know, there exists a Boost Counter that is relevant for the speed echoes. Its value can be 0, 1, 2, 3, or 4 (and so far it seems it cannot obtain other values than those). At the value 4, Samus obtains echoes. Now, you most likely also know about temporary BlueSuit travelling, which basically means that Samus has restricted options to move in order to avoid checks/updates by the game that the game can execute which would reset the Boost Counter from any non-zero value back to 0 in certain situations. The interesting part here is that the restricted movement that one knows from temporary BlueSuit travelling does not only keep the Boost Counter´s value if it already reached 4, but this movement generally keeps its value, even though one will not see any difference (since there are then no blue echoes visible if the value is only at e.g. 3).
In the video clip, via the TAS Super Short Charge input pattern, the first 2 taps (i.e. Boost Counter value 2) is achieved at the beginning, before the bombjump over to the isolated pillar of blocks. From there on, the next (3rd) Boost level is obtained on the spikes, where the 10 knockback frames that the spike-contact provides allow Samus to fully unmorph before those knockback frames end, to continue running. For the last Boost level, the spikes are used again, but less space is needed (since Samus´ animation, as in the change of poses, cycles through itself frame-wise faster, meaning the magic pose appears earlier), and in this case, Moonwalk is sufficient to provide enough space on the spikes and has the property to conserve the Boost Counter´s level when chaining it right after the unmorph, and when switching to forwards movement right after the Moonwalk.