they sell actual buckets called ROCK Buckets, they allow smaller things to fall thru, and just catch rocks
BUT Honestly, depending on how large the rocks, and or tree's and stumps
you might be better off renting a dozer and having them up root the larger things, a dozer with a ripper behind it does faster work and less abuse to your tractor

NEXT, depending the size of the tractor you have, they actually have devises you pull behind a tractor called rock pickers
depending on design,(one I use) is designed to be towed, it fills up a box with rocks till i then dump it, I dump in field, and and continue, this way you can just drive and get more done faster
I then have to come back and load up dump trucks with a loader

but its all a time consuming project
and depending how deep you go(or shallow) you will be repeating the task every yr or couple yrs
as both frost and plowing/dics-ing the field , will cause rocks to rise to the surface
my one 50 acre field has been rock picked for 40 yrs now, and always seems to be more the following yr< I swear it grows rocks
I had about 2 acres of tri axle dumped loads of rocks at one point from JUST this field, its crazy

both of these ways are NOT fast by any means, a rock bucket is SLOW going, a rock picker is WAY faster
and if this is a rather well grown up field, , a dozer, most likely will be a MUST have tool to get the field ready to be rock picked, and for sure the fastest way! if there are any larger tree/tree stumps or boulders!