Complex sentence: Roberts painted a considerable number of fine oil landscapes and portraits, some painted at artist camps with his friend McCubbin, but perhaps his most famous works, in his time, were two large works, "Shearing the Rams" and "The Big Picture".
Split into simpler sentences: Roberts painted a considerable number of fine oil landscapes and portraits, some painted at artist camps with his friend McCubbin. Perhaps the most famous in his time were two large paintings, "Shearing the Rams" and "The Big Picture".