Glyphosate products like Roundup QuikPRO - 5 x 1.5 oz. packs can have a chemical residual in the soil of up to 2 weeks so it is recommended to wait that time before planting in the treated area.
You will need to wait at least 2 weeks to plant any type of seed after using Roundup QuikPRO - 5 x 1.5 oz. packs.
Unfortunately Centipede grass is so closely related to St. Augustine grass that there is nothing that will remove it and not hurt the Centipede as well. In your situation it is recommended to spot treat the unwanted grasses with Round Up and kill it directly, and then replant Centipede in those areas.
We do carry many professional Round Up products