I do not have a lot of indoor space to start cuttings. I was wondering, what is the minimum temp that cuttings will tolerate and still root? I understand that ideally they like 70-80 deg. But I think I will need to start them on the back deck. I will be trying the root riot for the first time, and they will go into large clear Tupperware containers for humidity (humidity dome). If temps get below freezing I can bring them in at night but what is a safe temp to leave them outside? I plan on starting them in mid march, so that by mid April I can transfer them into containers. By that time temps are a little more consistent and I could cover with plastic (hoop house) if I need to. What temp is safe to leave them outside?

I'm not exactly sure, but I know that at 60 degrees they take much longer to root than at 70 degrees.  As far as rooting, it doesn't take a lot of space.  I put mine in a cabinet beneath a bathroom sink.  Temp averages about 72 degs and it's nice and dark.  Of course, once they are potted up, then they start taking up space.

Have you consider a heating mat or coil? We all have lost so many good cuttings, your best choice is to put them away for the winter in refrigerator...or for the sake of experimenting, you can put some in moss in  box /bag with some air, tuck inside of a black garbage bag and put next to a compost pile, or cover the bag wih leaves, and leave i alone... you may have a luck that we others don't. 

The plan is to either wait till march to get cuttings or store in crisper until march. I have a heating mat but managed to cook 200 cuttings last winter so I'm a little hesitant to do that again. I suppose that I could put them on the porch suspended over the heating mat by a couple 2x4's. If 60 deg is the magic number I'll toss a wireless thermostat in one of the bins to keep track. If it got down to 40 deg or so would they rot, or would they just do nothing until they warmed up?

if you have them on the porch, throw a blanket over. I don't think they will rot, but they might.

I think rooting cuttings is on one level a race against time.
the race is to get roots before the cuttings rot.
mold is everywhere, ready to start the process of decomposition.
so best to have ideal rooting conditions as far as temp goes, to give the cuttings their best chance.

Very much agree, Grant.
The best results will be with a consistent room temp.  Even if it's 60, they will root, but you don't want fluctuating temps of hot/cold, as this will encourage mold faster.

Ok. I think I've got a plan. I'll start to root them in Root Riot cubes in the closet with no light in late March. When I get roots I'll be able to transition them outside with hopefully no weather issues, mid to late April. It's 2-3 weeks later than I'd like but It's a balance of risk vs reward. I have very limited space inside and you gotta do whatcha gotta do. I'm jealous of all of you with grow light set-ups. Maybe someday. Thanks for the help.

it is race against time. that's why winter rooting can cause some issues. root in spring, and less issue. once root is good, leave them outside with night temp low as 50. anything lower than that will not help much. leave the cuttings on top of re fridge. or in washing room. or near water heater. somewhere the temp will be 70 or higher. when i used to brew beer during the summer, i would sit the carboy on the top of AC vent. keep the carboy at constant 70 or so with cardboard cover. put the humidity bin near the air vent during the winter will do similar thing.

you need a thermostat for your heating mats.

http://www.amazon.com/Hydrofarm-MTPRTC-Digital-Thermostat-Heat/dp/B000NZZG3S/ref=sr_1_1?ie=UTF8&qid=1384997708&sr=8-1&keywords=plant+heat+mat+thermostat