Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your situation, and wanted to help.
Oh dear, this isn't good. It may be that the cough possible infection or secondary to heart disease) started Rolo's signs but if he is off his good, this is more serious and not something antibiotics alone likely will fix. This is b/c being off food in this species often causes the gut to slow or stop leading to gastric stasis -- one of the few true emergencies for this species. So, with these signs, we need him seen now by a local or ER vet before this can progress.
I have to say that I am so glad to see you are already syringe feeding, keep that up (hourly) as that is so important here. But again this should not be blindly treated (and legally antibiotics would need to come from a vet who's care he is under), as he likely also needs to be on gut safe pain relief, pro-motility drugs, +/- antibiotics. So, again this is a case you dont' want to sit on. And while I appreciate its Sunday, I would note that we are quite lucky in this country. Many vets do have Sunday hours, so do ring around local practices. Else most practices have contingency plans for emergency care even when they are closed. Therefore, it is worth ringing the practice. If they are open, you can get in today. If they aren't, then they will likely have a message to direct you on contacting their out of hours service. And if you don't have a vet, you can find a local one via the RCVS Register (http://findavet.rcvs.org.uk/find-a-vet/) or Vets Now (http://www.vets-now.com/find-an-emergency-vet/) who are open all nights/weekends. In any case, if you wanted to get this checked out sooner then there are options to do so.
Finally, just further to syringing food, if he is off fluids, do make sure to address that angle as well. He will get some in what food slurry you feed but if needed you can also try tempting him with pedialyte (fruity flavors are best tolerated) or diluted Gatorade (50% diluted with water). A typical dose for animals is 4.8mls per 100 grams of body weight per day (obviously divided over all day drinking). This is his maintenance rate and it is a good starting place for supporting him against dehydration.