I spend some time wayfinding, then unlock the treasures with the following codes:
Roman Treasure:
9 0 0
Because:
As @Alconja said in chat: "Starts with the blue arrow and is inspired by this puzzle: The Sands of Time Produces the letters CM (or 900 in Roman Numerals)" and further demonstrated:
Thanks Alconja.
Japanese Treasure:
4 2
Because:
Using the clock-method I begin at the red arrow (since blue was Roman and it is said pirate is black) and navigate through some numbers, only to arrive at "ADD". Considering the numbers have meaning, as does the instruction to add, I go back to find my way, adding the numbers as I go... 10 + 1 + 16 + 1 + 14 = 42
Pirate Treasure:
2 0 (or 3 5)
Because:
Starting at the black arrow and using each cardinal direction letter as an instruction, I run into East twice, taking me to 8. At that point, I look around and find a path leading South, which leads me to 12 where the trail seems to end. Looking around again, I see the clearest trail is to the East. Following that, I then find a trail, where I think Roman's have been. Following it, I head south and encounter an instruction... A - D - D (- 1 - 5). At that point I hit the coast, and think, perhaps this is a clue the pirates setup as they wandered... I'll add 8 + 12, the #s I encountered before "ADD", to get 20. If that doesn't work, I'll add 15 more as the # I found after "ADD", getting 35. I head back to the pirate's chest to try it...