Roseola is something infants get.
Then we have the chicken pox and the shingles.
What made it so bad for my son was he came down with chicken pox close to his birthday while living in the house with his dad who broke out with shingles.
Then our son broke out with what seemed both chicken pox and shingles on top of it like a double dose of a dual virus.
I have no idea if my husband had roseola when little or if I did.
My husband never had chicken pox, he just got shingles when he was older about mid to later 30's and his sister did as well at the same time she also never had chicken pox.

My son does not have any mental problems, he does have seizures from time to time, rather odd ones.
Some times his arm just flies up into the air with big CorningWare glass bowl full of buttered pop corn, sending it all over the place.
Other times while holding a fork his hand and arm tremors and makes using the utensil more aggravating.
Then times he wakes up in the hallway not even remembering how he got in the floor in the hallway or how long he was down in it like that.

His dad had big issues with narcolepsy and cataplexy for years and years, got better with age which may wind up being worse as he gets even older.

I had seizures when I little, I would be walking with my aunt holding my hand and all of sudden would not have any legs or feet anymore.
It was like I only had a torso, arms and neck and head, without any legs at all.
I would just drop and could not get up, if sitting I would flop over and could not sit up.
Sometime it be like the lose of equilibrium and you could not determine any direction up or down right or left, you just free fall into undetermined space.

Hard to say what all viruses and such cause and what is inherited for sure.