After WWF purchased WCW in early 2001, there was serious consideration to having WCW resume operations later in the year as a seperate show with its own roster. But the timeslot didn't materalize and the Booker T vs Buff Bagwell test match on RAW was a failure with the crowd, leaving the entire plan shelved and giving us The Invasion instead.
But what if things had gone as originally intended? Vince McMahon acquires a time slot for WCW - probably either Friday or Saturday night - and relaunches it some time in the summer of 2001.
Your starting roster is limited to the contracts acquired by McMahon as part of the WCW purchase or picked up before the Invasion started:
Johnny The Bull
Chavo Guerrero Jr
Near the end of the year you can sign Scott Steiner (who was injured at the time of WCW's purchase) and other WCWers who were not initially picked up because of contract issues such as Bill Goldberg, Rey Mysterio Jr, Hogan, Scott Hall, and Kevin Nash.
Keep in mind that due to personal issues between them and Vince McMahon, the following would not sign with this new WWF owned WCW: Bret Hart, Jeff Jarrett, and Shane Douglas.
You might also consider shifting a few minor WWF wrestlers over to WCW.