I rooted and transplanted several cuttings of my fave potato vine. Brought it indoors and placed in front of a western facing window, in my laundry room. Figured this was the warmest room in the house. Past initial watering, I have not added more, but plants are declining. What am I doing wrong, got any tips so they can make it to April?

Not enough light?

All we can do when trying to shield tropical plants from winter is to give them the best approximation of summer weather as possible. If the soil gets dry, definitely water again.

The nickname potato vine is shared by several plants. Are you asking about an Ipomoea, Solanum, or something else? Here is a link to a search for "potato vine"
https://garden.org/plants/sear...

It's been more than 20 yrs since I had a Solanum type, but if it's Ipomoea, keep an eye out for spider mites & white flies. I've had those issues when saving Ipomoeas inside for winter. Alternately, if you feel like digging, it might be easiest to save the potato. IME doing that, there isn't much growth over winter, but as long as the soil doesn't get too dry or stay too soggy, the potato will wait for warmer weather and grow well again the next year.

Ipomoea

Purple, this particular ipomoea didn't have a Tuber. On the plants that do have a tubet, I don't bother and they return. It's just this one that I'm trying to propagate

It sounds like you are doing what you can.