Low roll are usually somewhat slow because there are too many of them for the system to handle
Not true, it is not about how the number of the roll but every rolls will be recorded in the database thus if a site dont "slow down" the speed for the dust roll then it will cluter up the database which means the house will need to do a database maintenance more often otherwise the site will be slower.
With that being said, if OP looks for a fast site without any restriction to dust bet then BetterBets is the fastest
while high rolls are fast as lightning, if you are low roller you might never notice this feature.
Does high roller even use autobet? Turns out that uses the autobet mostly is dust bet
You can try for dice sites with fewer people playing to reduce lag.
Number of player isnt the factor that slower down your bet solely