My biggest problem with roster only is the fact that it removes roll players and specialist from the equation.
It's easy to draft in the 1st round and get a potentially elite player but the roster is 53 players and everyone should have a purpose.
Example:
You draft a 88 speed LB in the 4th round and he booms +2 getting a 90 pass rush, 90 tackle, 75 strip but only a 22 M2M & 30 run defense.
In roster only I can put him as depth at WLB and hope for the best.
In a regular league, I can use overrides to make sure he only plays when the WLB is blitzing and bench him when the WLB is covering WR#5 or the worst possible WR#3.
The same goes for RBs who have 90 speed and 100s across the board for running the ball (ball carry/avoid fumble/break tackle) but he has a 12 pass block. Some plays call for the RB to pass block and in RO I'm obviously making him RB1 so he is on the field whiffing on the pass block plus risking injury for no reason.
I can easily name a ½ dozen other scenarios where in RO the depth chart and the plays called don't match the talent on the roster which becomes frustrating.
The A.I. is bad at controlling anything in MFN and it's my job to limit the amount of decisions the A.I. makes to include clock management at the end of the half/game and when/where to go for it on 4th down, not to mention 2 point conversations.
Anyone that has taken over a team that was run by the A.I. during free agency and the draft knows just how bad the decisions the A.I. makes. And RO basically says, let that same A.I. call all your plays.
If you enjoy it then that's great and keep playing it. My XFL league isn't for everyone because we have around a dozen elite owners and it's incredibly hard to compete but those days of empty speed players winning are long gone. You need great all around players to compete in the XFL as so many good owners have pushed each other to dig deeper and deeper into gameplanning and roster construction.
The biggest problem with RO as it stands now is anyone looking to join as an entry level league needs to quickly be made aware that the default player weights are so broken it can set you back several seasons if you build a roster using them. Actually, I think it's one of the biggest hurdles to retaining new owners overall in MFN.