You can find HM Strength south of Soleacon Town at the top of the Lost Tower. One of 2 ladies at the top gifts you with this.
Piplup is obtained as a starter in Diamond and Pearl or through trades.
trade it from soulsilver
Sorry, but Entei can not be obtained in Pokemon Diamond and Pearl itself, you must transfer it from old GBA games and use the Pal park in DP to catch him.
Put Honey on a tree
You have to migrate from Sapphire or Emrald.
Misdreavus cannot be obtained on Pokemon Diamond, so you must trade one from Pokemon Pearl.
The TM is roost but I don't know where to find it
look near rocks or evolve geodude
Transfer from Platinum, Pearl, or Diamond It was obtained from TRU event
The HM strength
Firstly its Darkry not dark cry and secondly its a Pokemon obtained by hacking pearl or diamond.
Sorry to say, but Gengar is not obtainable in the wild.