Roar's negative priority doesn't gel well with Mega Manectric's frailty and high Speed. Sure, Intimidate can compensate for the frailty, but Mega Manectric really needs its Speed to do its job effectively. Bulky Pokemon are better Roar abusers because they can actually afford to take a hit. Hidden Power (Ice) is also the ideal, and mandatory, coverage move because it lets Manectric hit Gliscor and Garchomp hard. Overheat also packs more power than Flamethrower; for example, it OHKOs Excadrill, while Flamethrower can't. While the Special Attack drop is detrimental, it can be solved by switching out. Mega Manectric is a straightforward and one-dimensional Pokemon because of this:
-Thunderbolt
-Volt Switch
-Hidden Power (Ice)
-Overheat
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Manectite
Ability: Lightning Rod
Why is Zapdos using a physical move when its Special Attack is clearly better than its physical Attack? This isn't R/B/Y anymore, when Zapdos would use Drill Peck to bypass special walls; that, and 90 Attack isn't the best attacking stat to use, especially when you're using a -Attack nature. As Nah already said, Zapdos is a better Roar user, since it can actually afford to invest in bulk:
-Thunderbolt/Volt Switch
-Hidden Power (Ice)/Defog/Roar
-Heat Wave/Toxic
-Roost
Nature: Bold
EVs: 248 HP/176 Def/68 SAtk/20 Spe
Item: Leftovers
or
-Thunderbolt/Volt Switch
-Hidden Power (Ice)/Roar
-Heat Wave/Defog/Roar
-Roost
Nature: Calm
EVs: 248 HP/64 Def/180 SDef/16 Spe
Item: Leftovers
Magnezone's biggest niche is trapping and eliminating Steel Pokemon with Magnet Pull. While Sturdy itself is a good ability, it's not worth giving up the aforementioned niche. What does Signal Beam hit aside from Hoopa Unbound and Celebi, really? Volt Switch gives Magnezone better utility, to be honest:
-Thunderbolt
-Volt Switch
-Flash Cannon
-Hidden Power (Fire)
Nature: Timid/Modest
EVs: 4 Def/252 SAtk/252 Spe (Timid) or 172 HP/252 SAtk/84 Spe (Modest)
Item: Choice Scarf (Timid)/Choice Specs (Modest)
Ability: Magnet Pull
or
-Magnet Rise
-Thunderbolt
-Flash Cannon
-Hidden Power (Fire)
Nature: Modest
EVs: 128 HP/252 SAtk/128 Spe
Item: Air Balloon
Ability: Magnet Pull
(note that while Air Balloon and Magnet Rise seem redundant together, this combination serves a crucial purpose vs. Excadrill. As Excadrill breaks the Air Balloon with a coverage attack, Magnezone uses Magnet Rise to maintain the Ground immunity for 5 turns, which is enough to let it KO Excadrill)
While Eelektross' Speed problems can be fixed with Thundurus' Thunder Wave, and while it has a wide move pool, it's not worth using. It's outclassed by other offensive Electric Pokemon (like Raikou) because of its meagre bulk, even with Assault Vest, and that bulk doesn't really mesh well with its Speed. Raikou is a better Assault Vest user because of its better special bulk:
-Thunderbolt
-Volt Switch
-Hidden Power (Ice)
-Signal Beam/Shadow Ball
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Assault Vest
And if you really need a physical Electric Pokemon, you can even have Thundurus go mixed if you don't mind the worse matchup against Mega Venusaur:
-Thunderbolt
-Knock Off
-Superpower
-Hidden Power (Ice)/Grass Knot
Nature: Naive
EVs: 68 Atk/188 SAtk/252 Spe
Item: Life Orb
Ability: Defiant
Will-o-Wisp is the preferred status move on Wash Rotom over Toxic, as it has excellent utility in crippling physical attackers. Pain Split or Rest should be used over HP Fire, as Wash Rotom needs recovery, no matter how unreliable it is:
-Volt Switch
-Hydro Pump
-Will-o-Wisp
-Pain Split/Rest
Nature: Bold
EVs: 248 HP/252 Def/8 Spe
Item: Leftovers/Chesto Berry