45 degrees will not be enough to keep them growing and I think at constant cool temperatures like that the plants will be weakened and should be kept dormant instead.

If you want to keep them growing, it will need to be at least 50-55 at night and warmer in the day, 40-60% humidity is adequate, excellent ventilation is a must, MH lights are better than HPS for leaf growth, 10 hrs a day should suffice.

My question is why do you want to create a high maintenance set-up for plants that don't necessarily need it? I overwinter mine as dormant tubers, I give them a headstart about 6-8 weeks before planting time, and they grow quickly once the weather warms up.

The original post said the 12x12 room the plants will be in is going to have additional heating. I don't have experience growing terrestrial plants under artificial light, but I have had good success with planted aquaria. I use compact fluorescent lighting. I would expect the photoperiod to be of at least equal importance to the type of bulb used. I would suggest 12 hours, as these are plants of a tropical nature. That said, I agree it would probably be easier to allow them to go naturally dormant and keep them mostly dry and above freezing  unless, of course, you're dealing with certain temperamental Alocasia species which refuse to break dormancy. In that case, I would aim for temps of 70-80°F with the lights on, falling to about 60°F during the dark cycle, and I'd try to keep the humidity as high as possible. Again, no experience with indoor growing, but those seem to be the climate conditions my Alocasia prefer.

Thanks for the input Xerophyte. I would prefer to just let them go dormant. I did that last year and lost quite a few of my alocasia. I left them in the pots moved them into my building and cut back on watering. However, many of them never came back from the dormancy period. Is it better to dig the tubers and use the same practices as the colocasia tubers for overwintering? What about the ones that don't actually form tubers?

Another question that I have is what seems to be the preferred soil mix for potting alocasia? I have used the Miracle Grow potting mix for most of them and they do very well while for a few species this mix tends to stay too wet, thus causing them to rot. Is there a mixture that does consistantly well with all species?

Is it better to dig the tubers and use the same practices as the colocasia tubers for overwintering? What about the ones that don't actually form tubers?
You certainly can do this, but there's no need unless the soil temps (not air temps) will be going below 50°F or so. The tuber is a storage organ so the plant can "hibernate" but regrow. Tuberless species are not adapted for this, so dormancy usually means death.
Is there a mixture that does consistantly well with all species?
As with most other aroids, your best choice is a soil that drains quickly but retains moisture. A mixture of 70% peat moss, 20% compost and 10% perlite (by volume) gives me good results. If you prefer to use commercial potting soils, you can lighten them up by adding perlite and/or peat moss.

how did you let your plants go dormant? the ones that don't form tubers or enlarged roots do not have enough resources to predictably survive a dormancy and should therefore be potted up and kept alive until the following spring. which species are you growing?