Thank you all for the information. I've usually been able to keep these minis alive for a year or two then they die. I cut it all back, it's liking it's sunny spot and it's looking like it's going to live.

I agree with AnneW. It is in shock and needs to be cut back significantly. Those roots are unable to support that top growth, for whatever reason.

But understand that roses are first and foremost OUTDOORS, Sun-Loving plants. They need adequate water but will drown if the roots sit in water. Drainage drainage drainage, and sun.

These decorative potted minis are often hothouse-grown, have no experience coping with changing weather or environment, including arid indoor conditions, and are expected by the sellers to be a temporary holiday trifle. Most won't last. If yours is the exception, it will be because it survived transitioning to become an outdoor plant, as nature intended.

What was the temperature where you bought your rose bush ? What temp where you gave your rose sun ? Any chance cats peed in your potting soil ??) TAKE IT BACK to where you bought it ask for a replacement with complete instructions for a larger pot and ask if a heat lamp is needed until warm nights are here to stay

Take out of the pot, wash the pot with bleach, let dry. Get all the soil off the roots you can by shaking, patting, etc. Cut the top back severely (all wilted areas plus 1" or better) after replanting in fresh new soil over a layer of small stones/chunky gravel.
Curb your watering!!!!
This could be a systemic fungus due to sitting with "wet feet"...stores are notorious for improper watering.
Or it might have got blasted with cold being near a door?
Either way, fresh soil, clean pot, cut way back & hope!

If it is just one stem, I would not worry too much. Although miniatures can lack health and vigour, especially deepening on how they are grafted/rooted, sometimes potted roses are just groups of cuttings, and are often not fully rooted .

I'm not an expert, but after some search regards to Brown Stems in the pictures, found these, hope helps :
[garden.org]
[homeguides.sfgate.com]
[gardenerspath.com]

Might be transplant shock, I don't know how ifx that.

Perhaps @Fernapple has some ideas!