Nice looker.....great 'mane'...though I know nothing about the breed. Mysunwulf has nailed it, really....but here's what I do after first looking to see what the breed standards are regarding ear/face length, wool etc..Ask to see progeny (assuming he has some), looks at his teeth (assessing temperament is pretty easy when you are trying to look into the mouth of a hunk of muscle and attitude)....the teeth will confirm his age and you can make sure he has no under or over-bite. Make sure his legs are straight....no bow legs or knock knees. Look at the general state of his hooves. Testicles....should be large,firm,equal in size and no lumps or bumps. Make sure his body condition is good....feel the muscle across the spine from the end of the ribs down towards the tail. Ask to see any paperwork re blood tests done to exclude diseases.
Best advice really, though, is take someone experienced along with you and buy from a reputable source.
Love the lambs, by the way, so CLEAN......over here we have persistent mud in the winter and that lovely clean look is gone as soon as they venture outside.