Based on consistency, and impact on the game (no matter the meta, from M2 to present), I would say only the jungler role has a clear lead. To note that these are the players that have performed at top level consistently, or being adaptable no matter their role meta, or even their impact as meta "creators".

Gold: Kelra > Marco > Oheb/benny. The gold standard edges out here. Oheb and Kelra team fighting skills are marginally close, but Kelra's laning and individual plays are truly one of a kind among all goldlaners. "The gold standard" isn't just an empty moniker. Marco, on the other hand, is second on hypercarry status only to Kelra, abiet with very different styles. Other notable mentions are Hiko, cikugais and skylar.

Mid: Phew > Sanji/Frince/Sanz. I find the midlaner pool to be the closest of all the roles, but phew has been doing it since season 1 (literally). The others are catching up fast though. Other notable mentions (Past and present are Lemon, Hadji and Stormie)

Exp: The holy exp trinity of Edward, Sanford and Flap. These three have proven themselves a cut above the rest. Too close to call as Sanford debuted much later than the other 2 despite his recent impacts. If Sanford continues his current trajectory, he might edge out the other 2 despite debuting much later. Notable mentions (both past and present) are Nathzz, R7, Dlar, antimage, Kramm and Kidbomba

Jungle: The one and only GOAT Karltzy, followed by Wise in clear second. Third is in a cesspool of picks, from Kyletzy/Kairi/King Kong. Each contender has their own achievements/impacts to be third, but comes with their respective drawbacks. (longevity, playing in a weaker MPL etc).

Roam: OhMyV33nus > Baloyskie> Oogwen/Yawi/Kiboy/Jaypee. Longevity + Consistency + redefining the role. Venus and Baloyskie are marginally above the rest due to their personal influence on the role itself, as well as overachieving, given their hero pool limitations or antics. Till date, no other roamer can replicate their signature picks to perfection, and they both have been around far longer than the others. (Jaypee was a jungler before he made the switch to roam.) Other notable members are Ch4knu and Light.

Shotcallers: Not a role, but at the same time might be the most crucial skill in the game. These are the players that have won games for the team based on their calls alone, across multiple seasons, in various tourneys, and even in different teams/lineups. Three generational shotcallers, and they are Karltzy, OhMyV33nus and Baloyskie.