If it is an issue of cost and ROI, then the city need to push for a roof, and the team needs to carry a lot more of the cost. From the city’s standpoint, they are going to get a ton more value out of an indoor stadium in the long run.
I would be curious too from a “football perspective,” which of the newest stadiums (esp in colder cities) are completely open air? The last I can think of is Met Life, but that was built in 2010 and in a very different sort of market.