Getting started on alfalfa

So I’m new to hay farming and was wondering what is the best way to get a field full of Knapp weed and mustards out so they won’t affect my alfalfa later on. I don’t want to disk the seeds in the ground and have them pop out later. I was thinking spraying couple times with roundup then disking and everything else. What do y’all think about that? Also what ratio of oats to alfalfa seed do you guys use?

Getting started on alfalfa