So for my roserade, I'm currently using one with the moves Engery ball, Sludge bomb, toxic spikes, and dazzling gleam with it holding a leftovers.
I plan on breeding another one for a better nature and ivs, what would work better with that moveset; timid or modest?
Depends on the format you use it in. We think you are talking about Singles because of Toxic Spikes.
Big news: Spikes + Sleep Powder is legal now. If you want to breed a Pokemon make sure that every move you plan to use is in the initial movelist so that you can swap them out when you like. Those two egg moves are obvious, but Roserade also have a lot of moves only the preevo can learn. Unfortunately you can only take four moves with you. Those moves you have to keep an eye on: Leaf Storm, Sleep Powder, Synthesis and Extrasensory are pretty neat for an offensive set while a defensive one has to juggle with Sleep Powder, Spikes, Toxic Spikes, Synthesis and Giga Drain.
Do not forget: The Pokemon can remember any move it had on level 1. You can force level-up moves form the preevo onto the set by having those on both parents.
As for sets:
Roserade @ Life Orb
Ability: Natural Cure
EVs Lv 100: 252 SAtk / 252 Spd / 4 HP
EVs Lv 50: 252 SAtk / 252 Spd / 4 Def
Timid Nature
- Leaf Storm
- Sludge Bomb
- Extrasensory / Hidden Power Fire / Sleep Powder
- Sleep Powder / Synthesis / Rest / Spikes
Pretty selfexplainatory: Leaf Storm is a nuke and Sludge Bomb is the secondary coverage. It sounds weird, but Dazzling Gleam does not offer coverage at all. Grass/Poison is walled by Steel as well as Poison types and they resist Fairy just fine. Extrasensory deals a bit more damage against Heracross and covers Poinson types like Toxicroak and Crobat while Hidden Power Fire hit through Steels, however, Hidden Power Fire is hard to breed on unless you have the correct parents and Extrasensory requires you to use the Rose Incense instead of an Everstone. Sleep Powder can be used on the third slot if obtaining either of the alternatives is too difficult.
The fourth slots is mostly filler. Sleep Power is powerful if you can catch a counter on the switch. If it is already used you can try healing or Spikes. Synthesis is classic healing while Rest has some synergy with Natural Cure, allowing you to fully restor your health and heal the status on switch - still it forces you to switch which is something to keep in mind.
Roserade @ Leftovers
Ability: Natural Cure
EVs Lv 100: 104 Spd / 164 SDef / 240 HP
EVs Lv 50: 108 Spd / 148 SDef / 252 HP
Calm Nature
- Spikes
- Sleep Powder
- Giga Drain
- Sludge Bomb
This is a fine role, too and is much less breeding extensive. As said, Sleep Powder + Spikes is the highlight of this generation. The speed allows you to outspeed Honchkrow and to put it down in time. If you need more recovery you can try to fit in Rest or Synthesis, but it is not really necessary when you can put them to sleep instead.