The reduction of your problem to an instance of SetCover is perhaps clear to you. We will show that the reverse is also possible, to formulate any SetCover instance as a binary integer program of the kind you are asking about, and this will establish that the resulting minimization computation is NP-hard.
A good survey of approximate methods for such problems (including rounding from linear programming) is given by Fatema Akhter (2015), "A Heuristic Approach for Minimum Set Cover Problem", where a modified hill climbing algorithm is proposed and its performance compared on a library of SetCover problems.
First let's clear up the notation used for the constraints, because what was written in the Question: $$m \text{ numbers of constraints in the form } \sum x_j \ge 1: j \in [0,n]$$
does not adequately distinguish among different constraints. For each constraint there should be a subset $C_k \subseteq \{0,\ldots,n\}$ of indices over which the sum is taken:
$$ \sum_{j \in C_k} x_j \ge 1 $$
For convenience we will refer to this latter constraint by its index subset $C_k$, so that the collection of $m$ constraints is $\mathscr{U} = \{C_1,\ldots,C_m\}$.
This $\mathscr{U}$ will be the universe of our SetCover instance, and the family of sets from which a minimum cover will be found is $\mathscr{S} = \{S_0,S_1,\ldots,S_n\}$ where:
$$ S_i = \{ C_k : x_i \in C_k \} \text{ for } i=0,1,\ldots,n $$
Note that the sets $S_i$ are in one-to-one correspondence with your variables $x_i$. Let a minimum cover $\mathscr{S}' \subseteq \mathscr{S}$ of the universe be found, and set $x_i = 1$ if and only if $S_i \in \mathscr{S}'$, $x_i = 0$ otherwise. A little thought should convince us this assignment minimizes the objective:
$$ Z = \sum_{i=0}^n x_i $$
subject to the constraints $C_k$, which amount requiring each subset $C_k$ contains at least one variable $x_i$ which is assigned a value $1$.
In other words we have described how to choose which variables $x_i=1$ so that their sum $Z$ is minimized.
With a little further thought and explanation, this reduction can be reversed so than any SetCover instance can be expressed as a similar binary integer programming problem. Going in this direction we are given a finite universe $\mathscr{U}$ which we suggestively write as a set of $m$ points:
$$ \mathscr{U} = \{c_1,\ldots,c_m\} $$
and a finite nonempty family of subsets $\mathscr{S} = \{S_0,S_1,\ldots,S_n\}$ whose union is all of $\mathscr{U}$.
Define binary "indicator" variables $x_i \in \{0,1\}$ corresponding to the subsets $S_i$, so that for any choice of subfamily $\mathscr{S}' \subseteq \mathscr{S}$:
$$ x_i = \begin{cases} 1 & \text{if } S_i \in \mathscr{S}' \\ 0 & \text{otherwise} \end{cases} $$
Now as before we ask to minimize $Z = \sum_{i=0}^n x_i$ subject to the $m$ constraints:
$$ \sum_{i \in C_k} x_i \ge 1 $$
for $k = 1,\ldots,m$ where $C_k = \{ i : c_k \in S_i \}$.
A feasible solution $x_0,x_1,\ldots,x_n$ provides us a cover $\mathscr{S}'$ of the universe through the settings of indicator variables $x_i$. That is, since every constraint is satisfied, each $c_k \in \mathscr{U}$ will belong to at least one $S_i \in \mathscr{S}'$. A solution that minimizes $Z$ will at the same time minimize the size of $\mathscr{S}'$, since $Z = |\mathscr{S}'|$.
Having shown that your problem, at least in the generality described above, is NP-hard, it may be of interest to point out algorithms for approximate solutions to SetCover which produce in polynomial-time, covers that are within some factor of the true minimum cover size.
In the context of a universe of size $m$, the greedy algorithm (choose at each step a subset $S_i$ which contains the most points not yet covered) produces a solution whose size is at most $\log m$ times the true minimum size.
The Wikipedia article on SetCover which we linked above gives reference to a fairly recent paper by Dinur and Steurer (2013) which proves that polynomial-time algorithms cannot give much better approximation factors unless P = NP. This is the culmination of various investigations, showing "that the greedy algorithm is essentially the best-possible polynomial time approximation algorithm for set cover to lower order terms."