What you need to know is that there are strict legal FDA type laws and rules about what you can and cannot use (drug wise) in food animals including cattle.
Anything that says on it "for use in cattle" and you follow the label exactly is within the law. For example if it says give x amount for 3 days in the muscle and you do that and follow the withdrawal time listed then there is no issue. If however, you give 5 times x dose for 30 days that is not within the law and a sticky wicket we can deal with at another time ;D
If by steroids you mean giving testosterone as an injection that is a no no.
However, the implants have a variety of compounds in them and most (I think) are some kind of broadly defined by the public "steroid". As long as you follow label directions you are OK. Somebody out there - chambero, DLD knows more about implants than I do.
OPTAFLEXX - is not a steroid - it is a beta adrenergic agonist (ie it stimulates beta receptors). It is the same compound as paylene (sp?) for pigs, ie ractopamine hydrochloride
Optaflexx is approved for use in cattle fed the last 28 to 42 days prior to marketing. If you feed outside of this window, it is illegal. Optaflexx can be screened for in feed, urine, or tissues. http://www.elancous.com/products/pdfs/optaflexx/opta_label.pdf