We can't answer your question with any specificity without knowing all of the facts. What roadsides did you perform? How well did you perform them? Was there a video? If so, how did you appear? What did the cop claim that you did in the report? I predict that it says something to the effect of "suspect exited the vehicle and steadied himself on the roof of the car with his left hand. Bloodshot eyes. Strong odor of alcohol which got stronger when he spoke. Swaying when he stood..." Cops often follow kind of a script so that they testify consistently from case to case when they can't remember the specifics on every case.
If the cop went to the trouble of arresting you for DUI, then he is likely to testify that you were showing visible signs of impairment. Depending on your particular judge, the particular prosecuting attorney, and the prosecutor's supervisor (because of the amount of leeway he/she gives to the prosecuting attorney in cutting a plea deal), your case could be broken down to wreckless driving or some other lesser included offense, dropped altogether, or may have to go through some motions or trial. There are many many variables in these matters. Too many variables to tell you your chances at beating the charge in an online forum such as this.
In NJ if you refuse to give a breath sample you will be charged with Refusal which basically carries the same stiff penalties as a DUI so nothing is gained by refusing. In fact, if you are not under the influence a sample may help. Having said that, the arresting officer needs to have reasonable grounds to believe that you were operating the vehicle under the influence. One thing to look for are the results of standardized field sobriety test, detection of alcohol odor by officer, etc. This may affect the officer's grounds to request a sample. Officers must also comply with certain requirements in securing your consent and/or refusal. Language difficulties may raise issues. You need to consult with an experience attorney to explore your options.
It all depends on how you performed on the FSE's. If you performed poorly, and the police officer videotaped it, you will have a hard time overcoming that. However, if you weren't stumbling over yourself, a competent lawyer will probably be able to get you a favorable result at trial.