ERJ170 Captain reports descending to 1900 feet prior to glide slope capture during the ILS Runway 05 at CYYZ after being cleared to 3000 feet until established cleared for the ILS.

Narrative

On the ROKTO 3 arrival into CYYZ we were at 7000 feet and ATC advised us 'cleared direct to DULPA and descend to 3000 feet until established cleared for the ILS 05.' By the time we were given the altitude it looked like we were going to be high so flaps and speed breaks were used to establish a better decent. When looking at the arrival earlier we had not noticed the crossing restriction at DULPA of 3000 feet because the location of the name and restriction is not located next to the fix. As we were approaching DULPA the First Officer looked at the approach plate and noticed we were within the 13.9 DME from YTP or inside the fix XIGAN which allows to descend to 1900 feet so he set 2000 feet. The DULPA fix is on the approach plate but it does not have the 3000 foot restriction on the approach plate. The needle was alive as we went threw 3000 feet I am not sure if we missed the altitude at DULPA or not. The FO was just going by what the approach plate said and that ATC had said 3000 until established. As we leveled off at 2000 feet ATC asked us to level off at 2000 feet until the glide slope and later told us the next time we come into CYYZ we should intercept the glide slope at 3000 feet. Later when we arrived at the gate we looked over the arrival and approach plate to see if we had missed anything and saw on the arrival where DULPA is at 3000 feet; but it was not anywhere on the approach plate. I believe if the arrival chart could be changed so the restriction of 3000 feet at DULPA was clearer that would help and I also believe DULPA at 3000 feet should be added to the approach plate.