I want to make a trip with my spouse, but our travel dates will be different on the return leg. We would still like to travel together on the way out.

I understand one known option is to do this with 2x one-way tickets for each, so that the initial departure could be on the same itinerary.

If we want to reserve this with round trip tickets however, is there a way to still make sure we sit next to each other on the way out? Or does that just require us to pay up for the right ticket level so we can pick our own seats, and then navigate/select the layout simultaneously?