I rode this trip on 24th January which is the middle of the wet season. After reading the notes on the last review he said to be careful during the wet season as there are a few river crossings that may be flooded.
The road to Cape Tribulation is all tarmac and a beautiful road after you cross the ferry ($8 one way). There is a discovery centre that's incredible, but be warned...it's $40. Defintely worth it.
After Cape Tribulation and until you get to Bloomfield, it's a gravel road and has 5 river crossings. They are not wide and I went through wet season and still crossed. Nothing higher than knee height, crystal clear water and easily passable. If there has been a lot of rain in the previous days, the crossings are probably not doable.
That being said, it's a really nice ride. The gravel is well maintained. It's a popular road for 4x4 drivers. The scenery is stunning, and plenty of spots to camp along the way ;)
After Bloomfield, it's back to tarmac and really nice. I would suggest a bit of caution though. Some of the corners are hard to see and come up fast ;P
this route is mostly sealed the only unsealed parts is from cape tribulation to wujawujal. this parts is especially beatiful though.
you will have to cross a few creeks on this 35km stretch on gravel riad which might be unpassable in the wet season or after heavy rain.
about 40km north of port douglas you cross the daintree river by ferry and from there you are awaiting an about 60km long ride through the oldest living rainforest in the world.
near rossvile you are passing an old historical hotel with camping area and cabins. thus spot is definatly worth stopping.