yahoofishkeeper,
I noticed that you were the latest member to register on bluecrayfish.com a few minutes ago...the site admin. should send you an email within the next 24 hours that will allow you to access the forum.
68 degrees F is just fine for an alleni---I would say that anything between about 50 degrees F and 72 degrees F is typically fine. I keep mine a little warmer...at about the mid to upper 70s most of the time.
The disadvantage to keeping it warmer is that it speeds up its metabolism; making it more active (feeds more, etc.), which makes it moult more, which in turn shortens its lifespan---by how much, I don't know.
I personally feel it's safe to keep it in water up to about the lower 80s...much higher will probably have adverse affects.
As for feeding...what are "rosies"? Minnows of some sort? If so, then I'd be careful about giving it feeder fish. It creates a mess, so you'll need to really clean up after it, and you never know what sorts of diseases and/or parasites you may be introducing to the tank...
That's why I'm too nervous to use "feeders." I keep other healthy fish in with my cray though, and so far he's not quite able to catch them.
I feed mine shrimp pellets. I haven't tried algae wafers yet, but it's probably a good idea (esp. to curb their appetite for live plants that you might have in your tank).
Hope this helps. You'll learn A TON about crayfish once you get posting on that bluecrayfish.com forum! See you there soon!
Big Vine