I have a Yeti with a 62 reg and want a roof rack but from what i've read the bars changed shape that year. My question is when? Is my Yeti the new shape or the old as it has a bearing on which bars I can buy.

I believe the only change was to how many fixing studs there are along the inner edge, for use with the OEM bars.  If you're using aftermarket types (eg Thule) then there should be no difference.

The Skoda roof bars which I originally bought (from a fellow Briskodan) for my 2010 Elegance fit my 2017 SE L just fine.  Weasley is correct that there is only one pair of rear fitment holes in the each roof rail on later model Yetis, rather than the three holes on the earlier models which allowed some flexibility in the distance between the bars.  But the bars still fit just fine so I don't believe that the shape of the rails is any different to what it used to be,