Don't beat yourself up about last winter. Had it been any other normal winter your roses probably would have done fine. The garage should do best for this winter. My tips are keep them off the concrete floor and make sure you water them at least once a month all winter. In the spring when they start to show signs of growth you may have to take them out during the day and back in at night until there's no more freezes or frosts in your area.

In a place that warm, they won't go dormant. If you can arrange a light setup - simple hanging fluorescents - it should work quite well.

if they are still outside, they are in the process of going dormant NOW. Roses in any pots usually do not do well outside because the root system is not insulated by the surrounding earth. I overwinter many dormant potted and tree roses in my garage, but it is not fully heated because I do not open the vents. At 35-40 degress, they have 99% survival rate. Can you open a window or something to keep it a smidge cooler. Dormancy also requires decreasing light. Try to mimic mother nature.
And i would not judge anything by last winter.
best luck and keep us posted