If you look up the CPUs on CPU Benchmark, you will see that an i3 of that generation is a wise choice. A i5 or i7 would be more expensive without giving Roon or you anything useful.
The single core speed (which is most important for Roon) of an i5/7 is not faster than an i3, and an i3 already has 6 physical cores, which is enough for running 6 zones in parallel with crazy DSP, and way more than 6 with sane DSP.
A 13th gen i3 is much more capable than, say, a 10th gen i7. Model numbers mean nothing.