the 30mm prob rolls faster than the 28mm - and a 32 might roll faster than both
unless you get carried away and reduce pressure too much
but of course there is a weight increase as you go up in size
( see chart above and link below )
https://www.bicyclerollingresistance...000-comparison
.
Don't want to start (another) tire width debate, but tests done in labs are only good in labs. Real world usage is another thing, and there are several other factors to consider than RR.