What is the fastest alternative route to getting certified/licensed for R.R.A. (Registered Radiologist Assistant)?

According to the ARRT website, it says I have to complete a bachelor’s degree

I would see that as the first clue. Yes you have a Bachelor’s Degree but it is not in the field that you are leaning toward now so that could make a major difference with how the nearby hospital will look at your resume. In some areas, hospitals will only hire staff with a Bachelors and aren’t interested in Assoiates. So, I suggest that you call the local hospital where you plan on working and talk with their HR department to ask the question whether they will hire an Associates for an RRA. If they say they prefer or only hire Bachelors, I’d then verify that your current Degree is enough to count toward their requirements. I’m going to guess that it won’t but I don’t know where you live and you’re better off discussing this with knowledgeable people from where you plan to work. I know that in my area, the hospitals shun those with Associates Degrees, but that might not be the case in your area. So, start by talking to the HR department where you want to work because it doesn’t matter what anyone else thinks—not even a different hospital