[WIP; if you saw this to give feedback, please just look at the linked collections, thanks.]

Surprisingly, searching the workshop, I didn't see any curated collection of road and highway collections.
While I encourage everyone to look through the workshop on your own instead of looking for or asking for "top" lists (y u gotta do the little ones like that? Smaller creators make good stuff too!), collections aren't what we normally look for, so here we go!

The collections in this collections are mainly meant to REPLACE most or all of the base game roads.
Usually this is because you want something more realistic, such as roads closer to your country's style.

This is important to note because many such road assets will NOT play nice with vanilla: colors or markings won't transition well, edges and barriers won't line up, and at worst, you get bright white tears and weird holes.

• WhisperWalks' Roads
  No collection, so here's a worship link with the Road filter applied.
  His top creation is his Tiny series of highways.
  With unknown eons of blood & sweat past the event horizon into what only network modders know as "nodespace," he managed to arise from the void with the magic to make markings render automatically in nodes.
  The Intersection Marking Tool mod kind of makes it obsolete, but you can beat automatic markings.
  His tunnels entrance even have graffiti you can toggle off if you don't want it.

Sorry, World, there are a lot of USA options.
We'll give only roads (not highways) their own section.

• BIG Urban Roads
  Despite the name, actually a full collection from small to large.
  Rendered tunnels!
  Non-ground versions are custom models.
  
  Required items: 3 - Markings, Traffic Lights, Railway Crossings
  
  
• Big USA Street Package Final Version
  Another option for USA roads.
  Seems more vanilla-like.
  Ground-only roads.
  
  There's an expansion set with unique options like cul-de-sac or dead-end roads:
  Big USA special-Street Package Final Version
  https://steamcommunity.com/sharedfiles/filedetails/?id=2038354006
  
  Required items: 0.
  
  
• North American Roads Liberated
  A few extra options, looks like vanilla roads made American.
  Mainly worthwhile for its roads with trees.
  
  Required Items: 6 - But all included in the collection.

• Sparky's UK Roads
  
• Korea Road Pack
  If you get the Hangang Expressway listed below, you'll want to add this Korea Bike Road by that author.
  
• ELVIS ROADS
  Actually roads with BRT lanes and props.
  
• Korean Style 10Lane Road + Overpass / Underpass
  More Korean roads with center lanes that can go up or down; usually for buses.

• Thai Road Project
  
• US Road Project
  
• UK Road Project
  
• Belgian Highway and a Suburb Stree
  No collection, so here's a filtered workshop.

• ANOTHER AMERICAN HIGHWAYS SERIES
  
• North American Freeways
  
• Big USA Highway package concrete version
  
• Big USA Highway package Final Version
  
• SHUTO Expressway
  Japanese
  
• Hangang Expressway
  Korean.
  The author also made this single Korea Bike Road, so you may want that too.
  
• Italian Style Highway
  No collection, so here's the workshop.

• Highways over Wall
  
• Sunken Highways
  
• Zoneable Highways
  https://steamcommunity.com/sharedfiles/filedetails/?id=2105507649
  
• 2 Dutch Style roads with bike lanes and a 4 lane vanilla road with bike lanes of alternative colors
  https://steamcommunity.com/id/abh02PC/myworkshopfiles/?appid=255710
  
• Highways with exit lanes, by Geowolf
  Seems more like an expansion to vanilla highways, but providing variants with exit lanes.
  Probably more advanced and best with detailing mods, so I chose to put them here instead of my NExt2 Replacement collection, that includes expansions to your vanilla collection.
  
  Similarly,
  
• Highways with signs of start and end
  Is pretty much what it says. Highways with a few extra props.
  Main thing is high speed segments with speed limit signs.

There are many other great road packs and collections, like highways with express or carpool lanes, various roads with tram or monorail, and so much more. These were just basic collections!

• Original Road Expansion Pack: mainly wide-sidewalk versions of vanilla or NExt2 roads, also by mytime0317.
  https://steamcommunity.com/sharedfiles/filedetails/?id=2399567675
  (available as a single pack here)