It has been this was all season. I don't remember issues last year, though I was so busy, I used my phone more than my Roku last season.
I could be wrong, but I think they have switched to 60fps video this year. I have noticed that when it does play well, it is great but it freezes so much now.
one solution I have found it to simply pause it and restart it. Works evertime. Until it does it again. Rinse at repeat. You may have to do that each inning.
Hopefully they fix this soon.