Dont understand weapon/shield handles...

Can i use them in roleplaying or only for pvp-only char? Where do i get them and can i add em to anything i want?

Sheild handles and wand wrappings are different from other weapon mods as they were prior to NF only existed as inherient mods to weapons. Therefore, shield handles, wand wrappings, and focus cores (unlike sword hilts, axe grips, etc) can only be applied to weapons from NF or GW:EN.

You can use them where you want!

You can tell whether a Handle (and an inscription) can be added to a shield by looking at the description text of the shield - if it says:
"Inscription: [description of inscription here]"
- you can "overwrite" the inscription (or salvage it) AND add/salvage/"overwrite" the shield handle. If the description doesn't say anything about an inscription, neither can be added and the shield is unchangeable.
The same goes for weapons as far as inscriptions go! Upgrades can be added/salvaged/changed on weapons as always!

You get inscriptions from drops: blue, purple or gold from NF or GWEN. Or you can buy them from people right here on Guru in the Sell section

Inscriptions (Wiki)
Upgrades (Wiki)

Cheers!