I found one big dead roach in my room tonight is it likely i have more?

i only ask b/c my landlord didn't put screens on all of the windows in my apt so one night i left the house with all the un-screened windows open and stayed at my bf's house that night came back the next morning and closed them all. i have never in the 8 months here seen anything aside from ants or a mosquito or a fly in the apt. those i'd much rather than the roach obviously. but in any event back to my question should i be concerned about more? or did i **** up big time by leaving the windows open and likely that is how it got in. also to safeguard myself what's the best way to prevent them and clean my room and apt to keep them away? PLEASE HELP ASAP