I'm not sure how the vet ruled out a stroke - I think it's still a possibility, and if so baytril won't help, although small furries can recover quite well from strokes just by themselves over a few days with good supportive care (fluids, good nutrition, warmth & comfort). If it is an ear infection hopefully the baytril will have an effect.
Please double check your baytril dose - hamsters (especially robos) are notoriously difficult to dose. You need 0.04ml of neat baytril oral per 100g of bodyweight, given twice a day - this works out at around 0.01ml twice daily for robos. This is a very fiddly amount to do so I dilute the baytril 10% and give 0.1ml. I'm sure your vet has worked this out but it doesn't hurt to check - if you're not sure how you can tell us what it says on the label and we'll try to help.
It's also a very good idea to give probiotic at the same time - I recommend AviPro Plus (available online here
http://www.noahs-cupboard.co.uk/ with prompt delivery, or your vet might stock it), this can be added to the normal drinking water and won't hurt the healthy one.
Make sure she's eating too - syringe feeding small amounts of baby food if need be (care no onions or garlic in the ingredients).
Fingers crossed, let us know how you get on.