If "Black Rose" is Special Summoned, both effects can be activated. Since they are not mandatory, they can be activated in any order, so activate first the effect of "Kidmodo", then chain "Black Rose". Every card on the field will be destroyed, then a Dragon from your hand can be Special Summoned.
"Dragon Ruler" is now the best Deck to run this card in. It is searchable by a banished "Redox, Dragon Ruler of Boulders", can be revived with "Debris Dragon" and is a perfect discard for "Dragon Ravine". It could also be discarded alongside "Redox" for its effect to Special Summon a monster from the Graveyard.
This effect can also be triggered with the effect of "Number 17: Leviathan Dragon", which can be made by overlaying this card along with the aforementioned "Masked Dragon", "Exploder Dragon", or even "Delta Flyer" (the latter even allows for easier Synchro Summon).