Rorari aren’t bad troops. You have to take into account that they have a heck of a lot more man in the units that Hastati. I use them as reserves, as long as you don’t throw them up against something nasty they will hold. Plus when on campaign they make good garrison troops due to their number of a cheap cost, plus if an attack does come they can hold their own.

I normally have 1 Rorari for each Hastati and I keep the regular troops numbers historic. Although after a few towns the Rorari are left to hold towns unless I can make some cheap troops in the town to do the job for them in.