Scout --- there is a girl who can fly and make sonic booms.... closest to scout i guess as she becomes the team leader for the explorers and there won't be anyone with "super speed" as far as i know.
well.... there is some witches who are physically crazy strong and faster then normal humans ( see Solider and Heavy ) but sonic the flying hedgehog is a lot faster than captain america.

Sniper ----There is a sniper witch. who can make a bow out of magic and make some pretty crazy shoots with guns later on as her magic helps her predict movements and calculate where to aim.

Soldier ---- could be pretty much anyone as most witches who survived are good at fighting because of the persecution, there is however a witch who´s power is to be a super soldier. her body enhancement magic makes her a godlike sword fighter who is important for the plot later on, and the sniper witch makes fun of her as she is considered a musslebrain but as bad as solider from TF2.

Heavy ---- would be one of the Tequila witches. they are group off 300 year old witches who survived until now by stealing and possessing the bodys of brainwashed super soldiers(not made by themselfs).
they are like the Soldier witch but weaker. the 300 years of experience makes up for it thought and unlike the Soldier who refuse to use anything then a sword, they are also ok with guns of all kinds.
they are super strong and can even carry heavy machine guns that normally would have to be tripod mounted by normal soliders.
The heavy Carries a machine gun that (according to him at least) wights 150 KG where a real one would be around 40-60, so i gusse it's a fair comparison right ?

Pyro ----- Anna, who else ? there is other witches who can control fire, but no one can match Anna once she learns how to control her power.

Medic--- there is actually a handful of healing witches Nana can heal wounds and later on when she gets a power boost even regrow limbs after comming of age.
there is however later on alot of other witches who specialises in different kinds of healing and recovery methods who have perks Nana dont, she can only heal wounds to the body.
there is also a witch who can turn into a sword that buffs other witches powers if they use her... cant forget the the Kritzkrieg medics :3

Engineer ---- is a bit of a hard one.... there is a witch who makes Electric energy thanks to magnets who later on powers a city single handed, one who can bend the earth and build houses and bridges out of rocks and mud. engineering is not a single subject.... but if you only look at mechanical engineering like the one in TF2. Anna our dear pyro actually moonlights as a master builder of machines later on when she learns blacksmithing with her fire magic that is broken beyond belief later on after she becomes an adult.

Demoman --- sadly there is no Megumin as far as i know. some of the Tequila witches likes to run around with what could be considered early versions of bolt pistols from warhammer 40k ( something like a guns shooting self propelled grenades) and are pretty much the heavy weapons squad and generally the elite soldiers who gets the biggest boom sticks. that said...... there is a witch who can transform into birds ( and bird like monsters ?) who along with the scout witch who can fly preforms sky runs and drops bombs and directs the artillery. ( scout witch cant carry more then 1 person or she gets slow and cant fly all that high. but the bird one can later on turn into a giant bird monster straight out of monster hunter game.

Spy --- Nightingale is a good choise as she can hide herself in "the colorless world" of hers.
(its not actually a perfect invisibility as magic detectors can still find her. but also it have other powers like not being able to be attacked unless the attacker have haki.... i mean magic power, walking through walls and also in "the colorless world", the only thing that have color is sources of magic and this is how she finds witches and can tell if you lie) there is however a good contender for the spy role.
a witch who can make herself and other people transform into anyone she have touched once in her life, voice and all. *coff* the king who killed himself was fake *coff*
both use daggers so it comes down to if you think invisibility with a ton of other perks is better than a perfect disguise for the spy role.