For the first part of your question, a clarification: the Romans did not invent shears in the 2nd century AD. We have many nicely-preserved examples of Roman shears, but the wool industry was intensifying already in the 2nd millennium BCE in Europe and Eurasia, and stone/metal blades are among the first tools developed by modern humans. We have many examples of human-crafted blades meant to separate hides from animals even in the Neolithic. The earliest evidence (to my knowledge) of wool-related industries in the Eurasian steppe, which would include shearing, is the Early Bronze Age, about 3300-3000 BCE. *Note that this figure is based on Soviet Eurasian chronology, which is probably too early compared to the chronology established by Western scholars. 2500-2000 would be the probable equivalent. Note that this is specifically for wool industry. We have a lot of evidence of herd animal processing (for skins) further back in time, into the Neolithic, including in Eurasia. The earliest evidence of the domestication of sheep is from Mesopotamia, about 4000 BCE, and sheep tech was probably brought to Eurasia via the Maykop culture.

For those with access, Sabatini et al. have a nice write-up, with many references, of the emergence of wool industry: Archaeological and Anthropological Sciences volume 11, pp 4909–4925 (2019). https://doi.org/10.1007/s12520-019-00856-x