I've been making rootbeer for a while now, trying various ale yeasts and bread yeast (when I was out of ale yeast). Some leave a strong after taste (especially bread yeast), but most left some aftertaste.
I asked at the local brewery shop and they recommended I try Muntons Dry Ale Yeast. So I bought a package and made up a bottle of rootbeer. I am impressed! The bottle was ready to be refrigerated in 3 days and there is no yeasty aftertaste. It might be the shorter 'brew' time, but I like the results. I'll be using Muntons from now on for my rootbeer needs.