Hmm, but I think printing and literacy would grow together. If the Romans have printing (and cheap paper, which is a whole new set of problems, but I'll assume for now papermaking came with the printing press), they can put a reading primer in the hands of every Roman citizen. Part of the reason it was only the rich children becoming educated in , say, 1200 Ce Europe was because they had to pay a scribe to hand-copy them a scroll of Euclid or what have you. With cheap books, any family rich enough to have idle children is rich enough to have literate ones. It would revolutionize everything.
That was certainly part of the issue; but I think there also was another, somewhat deeper issue; namely the will and the manpower to really build a mass-education system. In Rome, education was limited to the nobility in large part because educated slaves used to teach reading, writing, and other subjects were very expensive (which did have its part in driving up the cost of books). Education might not have been quite a 1% luxury, but 10% is probably not overshooting it too far.
Bear in mind, when I talk of education, I mean the sort of education which would eventually evolve into the famous classical education, comprising rhetoric, mathematics, literature, etc. To read and write was not too uncommon in Rome; enough men who could read and write and had no other job were willing to teach (it still wasn't a very high-class job) would teach in small towns; though even then, it was mostly the local gentry who made up most of the class. The printing press would probably have an effect in making the materials for a classical education more available to more people.
There's a somewhat deeper problem, of course, which is a cultural issue. I think it's worth mentioning at this point that many ordinary Romans and many slaves could read and write for the above reasons (in the Empire, the personal secretaries of many emperors and influential men were often freedmen whom these men trusted), but mass education of the commoner, and especially slaves, could easily open cans of worms which no Roman wanted opened. I think that if you want to reap benefits from mass education and printing, you would first have to overcome this wall. It took a very long time OTL, and needed the pushing of the Enlightenment, and the Romans have much more serious existential reasons to want to avoid this as much as possible, namely, if slaves and the very poor start to read and write, for how long until they use their educations to overturn their rightful place in the world?
