The device to convert other mod biofuels is the liquid distillery. I'm using one in my current world to convert Forestry biofuel.
One thing you really need to keep in mind in this is that you need to decide whether it's worth it to convert the stuff. Rotarycraft is very much a world of its own that isn't directly comparable with or integrates consistently with other mod ecosystems. For instance, putting one ethanol crystal into a gasoline engine (which gives more energy per ethanol than a performance engine without additives) and then trying to covert that power into another mod's energy, you'll be getting about... 70 MJ / 700 RF total. Per ethanol crystal. And you're supposed to get one crystal per bucket of for example Forestry biofuel. Right now in 1.6.4 you get 10, but that's a bug. But even with 10, that's 700 MJ / 7,000 RF you can convert back out of RoC to a different mod. Do you know how much energy it costs to make that single bucket of Forestry ethanol? About 10,000 MJ / 100,000 RF, and that's just the recipe costs in the fermenter and the still factored in. No farm consumption, no optional squeezer for fruit juice, no energy losses to power perdition in the machines and so on.
What this means is, you really need to think hard: does it benefit me if I'm turning something costing likely 11,000+ MJ into something that's worth 70 MJ? This may be possible, since Rotarycraft is also counting energy in a completely different manner. That single crystal does run the gasoline engine for 60 seconds, and that's enough to power any individual stage of an extractor, for instance. In fact, you can set it up so that 1+4 run together or 2+3 run together. It'll be slow, but it will complete multiple work cycles during those 60 seconds. Maybe as many as 10 if the fast stages 2+3 are running. Now try asking any machine running off of RF to complete 10 work cycles on 700 RF - usually it won't even do one.
So maybe it makes sense for you, but you need to have that application for ethanol where it benefits you in similar ways to just using it in their source mods. And you really, at all costs need to avoid a cyclic dependency loop scenario where you convert an outside fuel to Rotarycraft only to power something outside of Rotarycraft. This can even be an indirect loop, such as using a gas turbine to power the Forestry machines that produce ethanol that you then convert to Rotarycraft ethanol crystals. That would be a colossal waste of fuel value, equal to tossing out 99.9% of the energy you could be getting.
TL;DR is: the power systems are nothing whatsoever alike and converting power and fuels back and forth will screw you over royally. Only ever convert in one direction. Which one isn't so important, so long as you don't build a cyclic dependency.
