... at those 3 items.
1. the power to build roads, does that mean states can't do that?
It does not say "roads." Article 1, Section 8 says, "To establish Post Offices and post Roads." Post roads, for post offices. Get it? Remember, Article 1, Section 8 is what the feds can do WITHIN the states. Article 4, Section 3 says that the feds can do ANYTHING within federal territory (like the District of Columbia, but also any other federal territory).
2. the power tribunals inferior to the Supreme Court, does that mean states can't have courts?
Article 1, Section 8 gives the feds the power "To constitute Tribunals inferior to the supreme Court." Article 3, Section 1 says, "The judicial Power of the United States shall be vested in one supreme Court, and in such inferior Courts as the Congress may from time to time ordain and establish."
Article 3, Section 2 defines the jurisdiction of these courts.
Since their jurisdiction is OUTSIDE of state jurisdiction, the states are left to have courts for THEIR jurisdiction (but not the fed's).
3. call up the militia, does that mean the states can't call up the militia?
Yes, that's exactly what it means. But the states DO have a role.
Article 1, Section 8 says:
"To provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions;
"To provide for organizing, arming, and disciplining, the Militia, and for governing such Part of them as may be employed in the Service of the United States, reserving to the States respectively, the Appointment of the Officers, and the Authority of training the Militia according to the discipline prescribed by Congress;"
And, then we get to ...
The 16th Amendment, which says, "The Congress shall have power to lay and collect taxes on incomes ..."
You should read it sometime. You will be surprised by what it says -- and what it does NOT say, but that you think it does.