Unless Cruz agrees to support the nominee, which he currently refuses to do, then he should get zero time. If he does, maybe 5 non-prime minutes. Besides does he have anything meaningful to say at the moment beyond apologizing for his lies?
Mc Cain still waiting on those voters like Rove on Hamilton County in 2012
Or, we can just look for Cruz and Trump to act as adults and politicians and do what is in their interest, the party's interest, and the country's interest -- which requires, above all, that Hillary Clinton not become President.
A speech to the GOP convention by Cruz urging support for Trump could do much to unify the party and help Trump win the general election. After all, who better to make the case for Trump and sing his praises than the strongest adversary that he bested at the ballot box?
Such political theater is a staple of political parties. In 1976, for example, the fight between Reagan and Ford got nasty and sometimes personal, but, after losing the nomination, Reagan gave a stirring speech to the convention urging support for Ford. It helped unite the GOP against Jimmy Carter and contributed to a surprisingly close election.