Your child can go to daycare with the roseola rash as long as the child with the roseola rash has no fever.
If the child with the roseola rash has a fever then you should not send them to daycare because they could infect the other kids at daycare.
The virus that causes the roseola rash has an incubation period from time of exposure to the virus to symptom development from about five to 14 days.
So if your child has gotten has gotten infected with the virus causing the roseola and roseola rash then keep them home for at least 14 days from daycare.
Then after 14 days you can return your child to daycare as long as they have no fever.