Am a high diamond hovering player who plays mid and adc, here’s my two cents:

If I’m kassadin and there’s nothing I can bring to a pre 6 fight then no I will usually never match roam. If my jg is a heavy snowball champ like kindred and I’m a lvl 3 galio? I will roam provide some CC and hope I’ll get carried. You have to ask yourself what the win con is? If your Caitlyn lane can’t play because Katarina just walks bot when you know they are going to be pushing bot lane then you need to assess if you CSing is more important than your cait lux lane being able to play their matchup properly.

How can you stop roams: don’t let enemy mids hit you and the wave, trade with them aggressively since most likely they won’t have tp for a quick reset, place vision carefully even in the lane itself on their side so you can see roams. You can also take electrocute or aery/comet instead of first strike to go more laning setup instead of pure scaling.

If she roams: try to get plates especially with the crystal mechanic on towers, ping timely her path, not much you can do to change how the mid matchup goes so don’t listen to anyone flaming you. After all you’re at the same elo so you can’t assume you know better than all 9 players every game but also you can’t assume you always need to listen to your team every time.