When i use multiple blockstate variants, i can see the model with texture in inventory, but when i place the block, there is only a purple and black checkerboard.

My blockstate file:

 {
   "variants": {
       "facing=east": { "model": "testmod:road_block" },
       "facing=south": { "model": "testmod:road_block", "y": 90 },
       "facing=west": { "model": "testmod:road_block", "y": 180 },
       "facing=north": { "model": "testmod:road_block", "y": 270 }
   }
 }

Also, how to make a crafting recipe? I tried putting a minecraft recipe file to src/main/resources/assets/modid/recipes/ but it did not work.

Recipes are in the data folder, check how datapacks do them

Where exactly should the data folder be? Data packs have it in the main folder, but that doesn't work.

for the blockstate you need to replace testmod:road_block with testmod:block/road_block

Just tried that and it still doesn't work.

It’s unlikely this is a Fabric API issue. Have you tried the support channels in the Fabric Discord.

If you believe it is a Fabric issue, please provide steps/code to reproduce: block state JSON, model JSON, folder structure, block registration code, logs, etc. We can’t do anything but guess with what is given.