Roundtrip tickets used to be cheaper than buying two one ways. For the most part that isn't true anymore. One way tickets, at least domestically, do not usually raise the cost of a trip. Two one way tickets are usually the same price as booking the same flights in a single itinerary.
Still many people book roundtrip travel because of change fees.
Airlines are waiving change fees to give you confidence buying new travel right now. Without change fees one way tickets become more flexible. For instance,
It used to be that one way tickets were business traveler fares, while roundtrips were leisure fares. Together with Saturday night stays and advance purchase requirements, the roundtrip rule was one way airlines tried to separate out the fares they offered to inflexible business travelers who would pay more from fares offered to leisure travelers whose decision to fly is more based on affordability. Low fare airlines like Spirit blew up that model.
Let's take a look at some flights I selected at random (on the most frequent route that I fly). Austin - DC on American roundtrip is sure cheap right now as a basic economy fare. These are basic economy fares, but that doesn't affect the analysis.
Book them as two one ways and they are the exact same price:
You should price your itinerary both ways, as two one ways and as a roundtrip, to make sure you aren't paying more. When you aren't, as long as change fees are waived, I'm recommending you consider one way tickets instead of roundtrip tickets.