Robin (M), Klein and Roy Inherit Skills

I have 2 of 3 of these units, both of which I use on my main team so here's what I've been working with:
Robin (M): so much more amazing with skill inheritance:
Possible As) Triangle Adept; combos with Raven tome, giving him greater damage output against Red and Colorless (2 of the main types of heroes in-game)
OR Close Counter: Close Counter is only worth using on ranged units that can defend really well. Robin is one of those units.
Possible Bs) Bowbreaker; Effectively combined with Raven and Triangle makes him an absolute Bow-killing machine. OR Shurikenbreaker; helps him deal with Dagger users, but they're not as frequent. OR Desperation; gives Robin the chance to Double with his otherwise mediocre speed.
Possible Cs) Threaten Resistance; cause he can defend enough to be close to the enemy team OR Hone Atk/Hone Spd/Spur Atk/Spur Spd for extra bonuses for other teammates
Surprisingly, I've found that Swap is an amazing assist for Robin as it let's him increase movement while also getting other units out of range of things he can tank. His Special is already good as is.

And my main boi, team leader and mascot: Klein.
Klein has access to amazing skills as is, but does benefit from skill inheritance as well:
A) is fine,
B) Blue Tomebreaker; Quick Riposte is weird, as Klein has frail defenses and as such is not suited for counterattacking many units (ex: dies to Linde or Julia on Counterattack). Blue Tomebreaker exchanges that for an increase in defeating Blue tomes, which are the more prevalent tomes in the meta. With BTomebreaker, he can Counterattack Linde and kill her, and can use it to kill Robin on the offense (Tanky mages can be troublesome for Klein).
C) generic filler such as Hone Atk/Spd or Spur Atk/Spd as he most likely won't be in range for Threaten skills to take effect.
As an assist, I've found Reposition to work out well. I tested both this and Draw Back and I found with Reposition that you can combine it with a Dancer to let Klein be in front of your army, Dancer behind him, but both out of danger. So: Attack enemy, dance, Klein repositions Dancer behind them, both out of range (hopefully). Special again is fine, since it lets him kill units he otherwise wouldn't be able to kill in one shot.

For Roy, while I don't have him, here's what I'd recommend: Probably Fury + Desperation, with Threaten Def: Roy has nice defenses with Binding Blade, so he'll survive a couple of hits. Fury will help with that, and increase his damage output further. Desperation will let him follow up immediately, so he can focus on killing things without worrying about speed, which is okay. Threaten Def will substitute what Seal Defense did for him, by reducing defense on your turn. Not that different, but nets further kill potential.

To support that skill set, Ardent Sacrifice or Reciprocal Aid help in bringing his HP down while also supporting your other teammates. Bonfire, Vengeance, Luna, or even Pavise/Aegis for defense could serve him well as specials.

Anyway, hope this helps with your planning! :)

I have darting blow on Roy, which remedies his average speed.